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TYPE
Original Research
PAGE NO.
9-22
DOI
OPEN ACCESS
SUBMITED
22 May 2025
ACCEPTED
18 June 2025
PUBLISHED
20 July 2025
VOLUME
Vol.05 Issue07 2025
COPYRIGHT
© 2025 Original content from this work may be used under the terms
of the creative commons attributes 4.0 License.
Review: Theory of
Thermoluminescence &
Related by Reuven Chen
(Author), Stephen W S
Mckeever
Hayder. K. Obayes
Department of Physics Sciences, Faculty of Science Universiti Teknologi
Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia
Directorate General of Education in Babylon Governorate, Ministry of
Education, Baghdad, 51001, Iraq
Abstract:
Thermoluminescence is a phenomenon
observed in some materials when they are exposed to
ionizing radiation and subsequently heated, thereby
releasing light energy, as a result of the transition of
electrons trapped at or near defect centers from
metastable states to the conduction band. Thereafter,
the relaxed electrons recombine with hole vacancies in
defect centers associated with an allowed energy gap
between the conduction band and the defect center.
The light emitted is of varying magnitudes at different
temperatures as some deep trap metastable levels are
sequentially filled, emptied and emptied again during
the heating process. The sequence of detrapping and
recombination topography is a function of trap depth
and energy gap size. The presence of trap levels within
the forbidden energy gap of insulators or
semiconductors, are associated with defect centers
which arise from impurity ions or vacancies, whether
stoichiometric or non-stoichiometric. The TL response
has been used to investigate the nature of defect
centers and therefore defect center chemistry in a wide
variety of materials including those used as insulators
in semiconductor and electronic devices, luminescent
materials,
phosphors,
dosimeters,
catalysts,
thermoelectric materials, pigments, high-temperature
superconductors and phase change materials.
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Introduction:
The term thermoluminescence is a
collective term that describes the luminescence
phenomenon induced by heating a material which had
previously absorbed ionizing radiation either directly or
indirectly through the ionization of impurities such as
rare earth ions. TL has been successfully used for
information storage, as in photoluminescent color
centers, called radio-photoluminescent materials,
book-betting,
dating
of
archeological
finds,
environmental monitoring, beta dosimetry and nuclear
waste safety, to mention only a few applications.
Historical Background
Thermoluminescence is by no means a contemporary
area of research in solid-state physics. The first
observations of the phenomenon in materials were
performed in the second half of the 19th Century. As
always happens in the infancy of new areas of
knowledge, these observations were not followed by a
more systematic study of the observed effects. It was
only in the second third of the 20th Century that
interest in exploring in deeper detail the origin of the
effects observed in the beginning was taken up. From
that moment on, a long sequence of investigations
developed the field to a level of sophistication that
made TL evolve into a classical character in data storage
phenomena in bulk solids.
The first reports on TL were made in crystals,
particularly in potassium chloride and sodium chloride.
These crystals exhibited intense emissions even in the
spectral region of blue, something hardly observable
today for almost any TL material. Even so, the scientific
community at the time disregarded the results and did
not follow them through, mainly due to an apparent
lack of practical applications for such an interesting
phenomenon. In those early days, it was already clear
that some traps-for charge carriers-created during the
sample’s exposure to ionizing radiation (mainly soft X
-
rays) were complex KCl crystals with 2- or 4-fold
coordinated Al or Na ions, and probably holes trapped
at these sites.
Fundamental Concepts
1. Definition and Mechanism
Thermoluminescence (TL) is a type of solid-state
luminescence in which the emitted light results from
the thermal stimulation of a solid that has previously
stored energy through one or more stimulation of
ionizing radiation. TL can be also explained as a
consequence of consecutive steps: the first one is the
trap filling; the second one is the thermal stimulation;
and the last one is the light emission. The trap filling can
be associated to the electron or hole excitation from
the valence band to a localized state within the
forbidden band, to a band level or to a conduction band
level. The thermal stimulation must be understood as
the release of the electron or hole from the localized
state to the valence or conduction bands respectively.
The light emission occurs when the electron or hole
recombines with a partner of opposite charge, after
going to a localized level that is close to the conduction
or valence band, respectively.
The main features of the two ionization processes (trap
filling and thermal stimulation) allow to expect that the
TL phenomenon can be observed in any class of solid-
state compounds, without any special requirement on
their thermal, structural or electronic properties. This
compound can be at room temperature or at a very low
temperature when the ionizing radiation stimulates the
trap filling. In spite of these two features, at present, TL
can be only observed in a small part of the solid-state
compounds which until the present contain mainly
insulators with a high resistance, the most
representative being the alkali halides and silicate
crystals doped with metal ions.
2. Types of Thermoluminescence
The TL glow curves of most of the samples considered
to be TL solids exhibit structure and are composed of
several glow peaks overlapped or not. However, in
some very thin samples of highly translucent crystals,
the TL glow curves exhibit only one glow peak. These
particular samples exhibit the unique TL behavior, at
present termed as "one peak TL". As it can be seen from
the citations above, this type of TL group is not a
minority. In fact, considering all the cited words
literally, it is clear that the "one peak TL" group exhibits
a qualitatively different TL phenomenon. Due to this
unique "one peak TL" characteristic, it appears to be
worthwhile to review the main aspects of this TL group
in order to have a clearer picture of TL of real solids.
Definition and Mechanism
Thermoluminescence (TL) is the phenomenon of light
emission as a result of temperature increase of a
luminescent material after it is irradiated. TL is found in
many types of materials, but only some of them are
suitable for dating purposes, namely, natural minerals.
To be used for dating, a natural material must undergo
irradiation with ionizing radiation and then must be
subsequently
heated
in
laboratory-controlled
conditions to read the TL signal. For example, minerals
in the sediment of a river bed or of a cave, which are
regularly irradiated by cosmic rays and by terrestrial
radiations from uranium and thorium and their
daughter nuclides in the soil and the ceiling of a cave,
have TL signals that can be read and used for dating.
TL was discovered in 1914 by two scientists, who found
that mineral grains would emit light when heated;
however, the phenomenon received limited attention
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until
the
1950s,
when
several
researchers
independently established that there are fast
components of the observed TL signals and suggested
the use of TL for dating purposes. Three important
developments in TL research during the 1970s have
maintained TL as an important tool for archaeodating:
the introduction of infrared detectors to make possible
the absolute dating of TL signals on a days-to-month
time scale for short burial durations; the introduction
of various experimental procedures to give accurate
ages for fine-grained quartz; and the introduction of
thermal transfer techniques to reduce age errors for
coarse-grained feldspar. TL at the present is used for
age dating of ancient ceramics and hearths, as well as
for determining burial ages of sediments using
sedimentary quartz and feldspar minerals.
Types of Thermoluminescence
Investigations of the dyes and samples inside
thermoluminescence materials are possible due to
their luminescence spectral properties and their
amplitude-temperature curves. Different color centers
of thermoluminescence materials have specific
emission bands related to their luminescence centers.
The investigation of color center presence and
identification analysis can be achieved through the
analysis of emission band positions, shape details,
amplitudes, ratios of emission bands, and effect of
sample contamination. A common strategy for
thermoluminescence emissions used for needled laser
determination of its approximate content made of
carbonization of the organic laser dye solvent residue
and its employ of thermoluminescence detection with
reflected laser beam during physical cooling of
thermoluminescence.
According to the spatial origin of luminescence
processes, common thermoluminescence can be
classified to normal or intrinsic thermoluminescence,
impurity or extrinsic thermoluminescence, impurity
enhanced thermoluminescence, impurity band or
resonance
thermoluminescence,
and
laser
thermoluminescence. In addition to their respective
involvement in the visible spectral region, internally
located condensate vibronic states of luminescence
centers can be excited at room temperature with
frequency-doubled laser beam. Thermoluminescence
chronologically started first or they can intersect the
laser signal profile during excitation, respectively, with
lower or higher standard delays. Following the
observable features of the timer sensor behavior to
laser pulse, laser seconds, or microwave seconds and
thermoluminescence countrates investigation, the
appropriate thermoluminescence naturals can be
determined and applied for ecophysiological forensic
investigations, for example.
MATERIALS AND TECHNIQUES
1. Thermoluminescent Materials
The study of thermoluminescence (TL) began by the
emission of light due to the heating of solids that
absorbed natural radiation. The discovery of the
emission of light by crystalline salts doped with the
valence-1 element stimulated numerous investigations
of their photoluminescence and TL properties. Alkali
halides doped with activators such as the transition
metals and halogens emit visible light when heated,
and were used over many decades for scintillation
detection of low energy ionizing radiation, and in
various other applications such as light sources and
optical devices. In this book we restrict ourselves to the
TL effect, and initially to these early studies of TL salts.
Several decades later, TL was reported in silicate and
borate glasses, which comprise a variety of oxides,
especially SiO2 and alkaline earth oxides, molten
together and cooled to form amorphous solids. The
detection of TL in quartz sand gave birth to the
application of TL dating methods to archeology and
geology, and stimulated numerous TL studies of natural
and synthetic quartz. More recently, TL was discovered
in nanocrystalline and amorphous silica produced by
xerogelling silica alkoxide solutions. In later chapters
we will describe TL in vitreous and crystalline
compounds, polycrystalline oxides, insulators, glasses,
and other thin amorphous oxide films used in optics
and
microelectronics.
The
identification
and
understanding of the chemical and crystalline
signatures of TL species remain important topics of
ongoing research.
2. Measurement Techniques
The
radiation-induced
signal
acquired
during
measurements of TL, optically stimulated luminescence
(OSL) or photoluminescence processes in materials,
non-destructively
provides
insights
into
the
concentration of color centers within a sample. Such
measurements
usually
employ
a
commercial
luminescence spectrometer which contains a solid-
state detector sensitive to light, an optical unit for the
optical path of the emitted light, and a computer for
data acquisition and control, among other components.
These commercially available photomultiplier tubes
use a scintillator and a compact photodiode to
determine low luminescence signal levels in specific
spectral ranges. A second instrument employs a
charged couple device for spectral analysis, which are
sensitive to a broad range of wavelengths. Thermal,
optical, and radiative activation impact TL, OSL, and PL
measurements and must be controlled.
Thermoluminescent Materials
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Thermoluminescent (TL) materials must have at least
one forbidden energy gap to ensure the trapping of
charge carriers. For TL purposes these materials are
doped with certain concentrations of luminescent
activators. TL materials can be classified according to
composition; luminescence activation; or thermal and
luminescent characteristics. Most TL studies have been
made on the following oxides: Al2O3, BeO, MgO,
Mg2SiO4, MgB2O4, SiO2, SiC, and ZnO; phosphates: LiF
and Li2B4O7; and sulfates: CaSO4, lithium sulfates, and
strontium sulfates. Al2O3 and MgO are Al, Mg oxide
structural types, basically. Thermal TL reproductions
available are obtained for single Cr3+ ions or Cr3+
aggregates in Al2O3 crystals, which are classified as
phosphors. TL materials were initially used in
archaeoluminescence and recently applied to space
dosimetry and bioluminescent studies. TL properties
are important parameters in dosimetry, such as
sensitivity, reproducibility, absorption characteristics,
presence of undesired TL signals, optical thermal
bleaching, minimum detectable doses, or read-main
time stability, as well as thermally and luminescent
correlated TL characteristics.
Currently, TL materials are widely investigated because
of their number of commercial TL doses and
luminescent photon detection system applications.
Recently, commercially TL materials have found new
applications
in
mapping,
photographic,
and
phosphorescent luminescence TL studies. These
dosimeters have low sensibility and resolution because
their reading systems are not optimized. Commercial TL
preparations can be processed to decrease impurity
effects. Optimum performance can be obtained by
using TL systems optimized in sensitivity and reliability
according to TL sample properties.
Measurement Techniques
Numerous methods for making TL measurements have
been developed over the years, the most significant
variable in a TL measurement, other than the quality of
the powder or crystal to be measured, is the extent of
readout control which is provided. Temperature
control over TL readout is important in accuracy and
reliability since the TL effects offer a rich source of
information about the materials, particularly in any
detailed study of their kinetic and spectral parameters.
Quality TL measurements lead to a choice of
measurement conditions, which must be in accordance
with the detailed kinetic model, and care should be
taken to avoid artifacts due to inadequately controlled
conditions. TL measurements are performed in a large
variety of devices which can be divided into two
principal classes: those which measure light emitted at
one temperature under isothermal condition and those
which analyze the glow-discharge curve. Several
isothermal glow-discharge curve and isothermal TL
measuring devices have been realized in various
versions, and different quality levels may be found. TL
studies may be carried out both in laboratory testing
and in-field environments, and laboratory-based
thermoluminescence instruments are widely used for
retrospective dosimetry.
Good temperature control is important in any TL
measurement especially if TL data are to be interpreted
in terms of the kinetic parameters of the processes
involved. Since the TL emission is produced through
thermal detrapping of charge carriers, any uncertainty
in the temperature history during measurement
procedure leads to uncertainty in the trapping
parameters. Unfortunately, many TL instruments do
not provide sufficient accuracy in controlling the
temperature. In many commercially available TL
readers, temperature is controlled through a closed-
loop feedback mechanism. Such feedback systems
typically work to an overall accuracy of 1°C. Given the
width of trapping peaks observed in natural samples
often ranges from 1 to 10°C, such a temperature
accuracy is inadequate for kinetic analysis. Also, many
TL devices use ceramic heating elements that need a
long time to stabilize near the programmed
temperature which removes the possibility of working
in a truly isothermal mode. At present, only a few TL
systems based on optical fiber temperature sensors are
able to work in a truly isothermal mode.
Instrumentation
The instrumentation necessary for the measurement of
TL is quite simple. First of all, a controlled heating
system is necessary. In usual TL laboratory work, we
employ a commercial furnace that allows a satisfactory
thermal homogeneity; for field studies, we must resort
to specially built heating systems. Sample heating must
not be too fast, but there are no strict limits on the
heating rate. This parameter can affect the glow peak’s
height and position, and even change its occurrence.
The use of high heating rates causes the peaks to shift
toward higher temperatures, this is the so called
“kinetic shift.” The heating ramp used must guarantee
a good quality thermal signal during the measurement.
The signal emitted during the TL signal is very weak:
good detectors must be used. Traditionally, TL signals
were recorded using a photomultiplier tube with a very
sensitive photocathode coupled with a glass or quartz
window filter that transmits the visible range and is
optically coupled to the photomultiplier. To protect the
instrument against stray light, a careful arrangement of
the heating and recording systems must be used. The
gain of the detector must be adjusted to keep the signal
within the linearity range, even if, in the case of a bad
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adjustment, the signals could still be used as age
advisors, in the case of dating low sensitivity materials,
at least within probable errors. Another traditional
recording technique employs a silicon semiconductor
detector with an appropriate filter connected by a
transistor or amplifier circuit to a suitable computer.
The main advantage of this system is its very high
detection efficiency. A few other recording systems
exist that are rarely used in thermoluminescence work.
THERMAL TREATMENT AND GLOW CURVES
Thermoluminescence (TL) intensities depend on
thermal treatment. Generally, TL objects are treated in
order to remove the shallow traps responsible for the
stimulation of TL at low temperature (annealing) or to
fill with electrons the deep deexcitation traps at high
temperature (activation). Low-temperature annealing
at normally several hundred °C removes the TL at low
temperature while it may enhance the TL at high
temperature depending on the spectrum of residual
thermal stability of the deexcitation traps. Harsh heat
treatment of several hours causes destruction of TL.
Each TL peak is either due to related deep deexcitation
traps or of the related shallow traps, and has particular
band structure for the related deep and shallow traps,
respectively. Heating rate is normally of the order of 0.1
°C/s. Excitation of TL is normally of the order of 10 3/s.
TL intensity is shown against temperature or its
logarithm, or time. The glow curve can show main and
sub peaks at the same or different heating rates for
non-continuous or continuous filling as well as
deexcitation processes. Multi-peak slopes follow the
multiplicity methodology that there are one or several
thermal resistances in the step of filling or deexcitation
processes of TL, respectively. Separated peaks with tail-
to-tail distance at least of 2
–
3 × 10 0 °C distinguish the
main and sub peaks. A substance has definite
characteristic thermal stability. TL of the same type of
atoms in crystal lattice has similar glow curve shapes
due to similar thermal stability. The corresponding glow
curve shapes forming the spectrum of thermal stability
are used for the characterization of TL. Low-energy
luminescence centers of the deexcitation traps are
used as tracers or markers for crystallization or
nanocrystallization processes. TL can be used for
comparative diagnosis of the lattice of common
transparent
crystalline
minerals,
accumulatory
sediments, etc.
1. Heating Rates
Temperature is a key parameter that influences
virtually all stages of TL. In fact, it has a crucial role in
inducing electron excitation and transfer, as well as the
subsequent recombination process over different
energy traps. The inductive and transfer functions of
temperature are often referred to as the "inductive"
and "transfer" temperature functions, respectively. The
thermal treatment applied to TL samples is usually
performed in a heating furnace, as there is an
appropriate control of the applied temperature or its
variation over time. Commercially available TL readers
can be configured to apply different heating rates to
the high temperatures stimulated sample. Most TL
studies employ heating rates between 1 and 15 °C/s.
Lower heating rates usually increase the TL signal, but
can lengthen the duration of a TL measurement to
several hours. As an alternative to heating rates used in
TL measurements, physics labs performing TL
measurements may opt for lower (or high) heating
rates, which can be adjusted in diverse TL experimental
setups.
In addition to α, a structureless parameter showing no
evident variation with heating rate, few TL analytical
expressions modeling TL glow curves have also been
able to provide good results for some glow peaks. Most
TL glow curves obtained for different heating rates and
for different experimental conditions display a
systematic shift of high temperature TL peak positions
with respect to low temperature TL peak positions.
Glow curves for kinetic order higher than one (or lower
than one) shifts towards lower (higher) temperatures
with increasing heating rate. This anomalous heating
rate effect is usually called "time
–
temperature" effect
in the TL literature. TL glow peaks correspond to first
derivative maxima of glow curves. Typically, TL glow
peaks correspond to the maxima found in the
derivative of TL glow curves. However, this statement
is only valid for a very short approximation to the TL
function performed under very high heating rates
conditions, that approach the so-called "infinite
heating rate".
2. Analysis of Glow Curves
The study of TL phenomena is normally made by
analyzing and interpreting glow curves. These curves
are complex in shape and their analysis and
interpretation is usually difficult and results sometimes
controversial. This occurs because TL usually does not
obey simple kinetics equations and may involve TL
signals from various interacting traps and even the
presence of different dopants. Even so, in some cases
when less complex systems are employed and the
experimental conditions carefully selected, the
simplistic analyses of TL signals using first order kinetics
equations can be made.
The deconvolution of glow curves is then often
performed by using glow peak areas in the simplest
method that employs the equation dI(T) = a(T) H(T) +
b(T). In order to analyze those glow curves, one needs
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to obtain a good temperature dependent second
derivative representation of the glow curves. The best
is to obtain it by dividing the original TL data by the
temperature dependent loading factors a(T). It can
therefore be fitted using a polynomial function or
directly from dI(T)
–
dI(T) plots. However, these
methods emphasize the relative positions of individual
features of glow curves - not their absolute
magnitudes. The temperature at which the first peak
appears - T0 - and the temperature at which the last
peak appears - Tn - should normally be indicative of the
range of DOS values. Alternatively, the second
derivatives had been processed by a principal
component analysis, followed by an AMUSE analysis to
orderly construct dI/dT(T) plots, assuming they were
available only for a fraction of the glow curve
temperature interval. The obtained principal and other
transformed component plots should be mixtures of
DOS, at least if the glow curve were a linear
combination of component peaks mathematically
curved to approximately Gaussian shapes and align
along the second derivative curve.
KINETIC MODELS
Abstract. Thermoluminescence (TL) glow curves
typically present distinct structure and only in the
simplest cases a complete description of the TL kinetics
can be achieved. The unambiguous extraction of the
kinetic parameters from glow curves is a demanding
task for both theorists and experimentalists. Regardless
how challenging this task may be, it is indispensable for
the elucidation of the trapped charge carriers'
properties and the electron-hole pair recombination
and emission processes. In this chapter, the kinetic
models applied for the description of TL glow curves
will be introduced, starting from the models that only
consider the kinetic processes occurring at a single
temperature and arriving at those that take into
account the multiple temperatures at which trapping
and recombination occur. These models will span from
very elementary to complex considerations about the
TL process, and will also introduce the concept of order
in rate equations. Since the kinetics of TL involves the
thermal stimulation in an open system of confined
particles, it will only be logical to discuss those
elementary systems that have survived the thermal
evaporation.
Kinetic Models
The glow curves, as they are regularly recorded in
unusual types of TL experiments, seem to agree well
with equations that correspond to the kinetics of a first
or a second order irreversible reaction. The irreversible
nature of the thermoluminescent process has been
usually taken as evidence that the electrons are not
simply thermally freed at the temperature at which TL
is taking place but that they are also described by
diffusion equations that would be thermally invoked at
much lower temperatures. The proposal of trapping
levels made it possible to describe the kinetics of TL and
other open systems of confined particles at finite
temperatures by models that are fully argued. These
equations have been further extended to account for
general competitive multiphoton absorption processes
that are described by explicit quantum mechanical
derivations.
1. First Order Kinetics
The first to elaborate on the detail of the influence of
heating rate upon the TL glow curve shape, in particular
why first order kinetics gives a straight line in a
particular plot, were Lattice and Reichman. Not all the
natural TL curves can be regarded as first order kinetics.
It has been assumed that the TL curves are around first
order kinetics, that is the curves could be converted
into a straight line, Log versus Ln plot. This assumption
happens to be correct for some samples with simple TL
curves but does not apply for others. Since most of the
natural TL curves observed could not be evaluated
within the above frame, the values of the kinetic
parameters are not generally interchangeable. The
complexity of most TL glow curves has already been
discussed and is the result of radiative and thermal
transfer processes. It can be however useful to treat the
TL as first order kinetics and we still consider the TL
characteristic of these kinetics. The rate of change of
the quantity L of TL emitted may be written as the
equation of a first order reaction, where L = L(T) is the
temperature-dependent rate constant of the process,
and dL/dt is the time rate of change of the TL response.
The constant L tends to increase with temperature,
passing through a maximum value around the
temperature of maximal TL intensity, after which it
decreases rapidly again.
2. Second Order Kinetics
One of the foremost principles of thermoluminescence
is that, if the trapping sites are in very low
concentration relative to the number of activator
centers, they will be filled as they are created in the
transition. For this case, one assumes that the activator
is in excess, and that the trapping sites are being filled
in a very slow sequence, so that the transition rate
might be written dI/dt = −W·I − dD/dt = +dD/dt = 0 for
the activator, and thus J0(n) = W·I where n(t) = n0 =
const. for the trapping. The formula for the current
becomes dI/d
t = −W0·I, which is the linearized solution
of the exponential statement of what must evidently be
a second order reaction in I.
To go to the next order in the trapping, one notes that
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there is condition 0 < n0 < Nt, where Nt is the number
of trapping sites in the system. This allows a correction
to be made to the previous treatment of a reaction in
which both n(t) and I(t) are severely shrinking, which
assumes n to be a very small constant, for a reaction in
which n is small but not nearly constant, although still
always much smaller than I. If we wanted a
thermoluminescent version of the work on
thermoluminescence where D is treated vaguely as
constant in the derivation of the current while the
surface is optimum for the pure exponential model, we
could consider it an easier calculation.
3. General Kinetic Equations
It is apparent from the earlier discussions that a critical
point in the TL, and in general all thermal activation
processes, is the part of temperature had been
implemented. The analogy with other thermal
activation processes leads to reconsider the Arrhenius
law and rewrite as:
k = Ae^{-E/kT}
with k the reaction rate, k the Boltzmann constant, and
A the pre-exponential factor. This gives as a
consequence the Arrhenius Law representation as Ln
(k) = -E/kT + Ln(A). This gives an easy way to find E, in a
plot of Ln(k) against 1/T. In addition, the pre-
exponential factor, A, was formally considered a
constant. However, increasingly in the TL community, A
has been considered a further dependence on T and
not a constant. More precisely the formula could be
written as:
k = A(T)e^{-E/kT}
from which, in principle, A(T) = k eE/kT could be
extracted by simply dividing the reaction rate by an
exothermic factor containing the activation energy.
Although considered in principle as an approximation,
A(T) = aT is one of the most used in the literature, where
a is a constant of the order of magnitude of 10−12. In a
general context, k was replaced by a more general
factor Q(T). Q(T) encompasses various variables such as
the temperature dependence of TSL signal, dose-
response curve, and other temperature-dependent
experimental variables.
APPLICATIONS OF THERMOLUMINESCENCE
Applications of thermoluminescence (TL) are widely
based on its function as a dosimeter for ionizing
radiation exposure. Most of these applications are
mainly IL. However, in archaeology, it is used first to
determine the time of firing of heating materials - bricks
or ceramics, to be sure that they are not older than age
- by TL dating. A few physicists use TL to measure quartz
sand grains to know the time of burial of sediments by
aeolian or fluvial actions, to estimate the frequency of
earthquakes along faults for paleoseismic studies. A
few more have searched for TL in weathered grains on
rocks and paleoraxis probable direction of the Earth
magnetic field reversals.
Thermoluminescence is also used in archaeology to
date wooden artifacts by using the cutting through the
steinwood to take heavily dended TL quartz powder for
dating. In other fields, TL is widely used to survey
residual doses of teeth and jawbones by dental X-rays
in forensic medicine. It is used to analyze collected
ashes in fire crimes in criminalistics. It is also used in
medicine as a substitute for SECs in an emergency dose
recorder for continuous in vivo monitoring due to its
peak warmup time dependency. Last but not least, TL is
used to analyze surface events of planetary bodies like
the Moon, Mars, and asteroids, due to their degassing
and weightlessness in outer space.
All the above applications, except for archaeology, used
actual TL signal response. For archaeology, both TL and
IL dating are combined using correction factors with
special conditions. Three TL properties have been
exploited for dosimetry and monitoring: Their surface
sensitivity due to the dose gradient near the surface,
their shallow TL glow peaks, and their dose error due to
the readout temperature. The shade and light of the
sample reflectance at the TL measurement wavelength
are different for excited indigenous color centers at the
div surface and excited natural color centers in its
bulk.
1. Archaeological Dating
Thermoluminescence (TL) measurements can provide a
dating method for anthropological and geological
phenomena. The TL dating uses the traps that were
filled with electrons during the exposure of the control
volume to the geological or environmental background
radiation. The exposed volume is assumed to be a small
volume of the bulk material. Because the typical TL
curves are related to the burning of the outer surface
by thermal activation, the concept of TL dating is
severely challenged. TL dating underestimates the age
of the exposed material because it takes an uncertain
time, usually longer than the exposure time of a larger
control volume, to burn the smaller grain.
Nevertheless, TL dating has turned out to be reliable,
especially in the dating range older than when the TL-
derived ages are validated by cosmogenic nuclide
dating. TL dating of pottery or bricks provides secure
dating with an accuracy of several decades.
The first archaeological TL dating was made in 1973.
The TL method was enabled because of the
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systematical measurement of the TL spectra and the
discovery of a reliable TL peak that dated to about AD
940. Two years later, the TL dating was first applied to
date pottery. Consequently, the TL dating was
popularized in the archaeological community as an
auxiliary method for reliably providing an ancient burial
age. TL dating has stimulated various TL-related
developments in terms of TL theory and experimental
techniques. TL dating has the potential to sufficiently
expand the time range for determining burial age. The
improvement of TL dating largely depends on
technological progress in conjunction with advances in
TL theory.
2. Dosimetry
In 1958, the concept of using thermoluminescent
phosphor materials (TLD) for radiation dose measuring
and monitoring was first published. In the following
years, several basic studies confirmed interesting
properties, confirming the unique and interesting
characteristics of thermoluminescent dosimeters. Since
then, several thermoluminescent phosphors were
synthesized with an easy-to-implement synthesis and
capable of being applied at several conditions such as
TLDs for high-energy radiation, radiation monitoring,
etc. The most famous TLDs are LiF:Mn, LiF:Mg,Ti,
LiF:Mg,Cu,P, CaSO4:Dy, or Li2B4O7:Mn are the most
common TL materials. These phosphors have been
heavily used as TLD in medical, space, industrial, or
environmental areas, especially gamma or beta
radiation.
There are different TL dosimetry systems, including the
TLD-100 and TLD-200, the PANDA system with
LiF:Mg,Cu,P. One system has been commercializing
TLD-100 for several decades without significant
improvements in its technology. The TLD-100 is a
naturally occurring phosphor KCl doped with 5 mol% of
brine is used for dosimetry at high doses using LiF:Mg,Ti
as the TL material. However, after these decades, a lot
of researchers were focused on improving the
sensitivity or characteristics of the TL materials,
introducing new materials prepared by dope, co-
doping, and codoping, and investigating new
techniques in TLD systems (fibre optic techniques, TL
reader systems, radial TL techniques, LiF doped, LiF
poled with metals). Researchers also improved the
commercialized TLD systems introducing them doped
by metals. New techniques on TLD systems and LiF
doped or LiF poled by metals were also published.
Among these materials, Li2B4O7:Mn seems promising
thanks to its properties, reducing the amount of non-
dosimetric effects.
3. Environmental Monitoring
The effects of uranium and thorium on the human div
have been extensively researched, and the conclusion
is that they are environmentally detrimental and
human carcinogenic. Although the most common
uranium tailings are yellowcake products characterized
by a large amount of uranium and little or no radon
content, mining should be avoided due to the
radionuclides leaking into the oceans and rivers from
the hydrological cycle. Radionuclide emissions are
known to have adverse effects on human health, and
regulating activities at uranium mining and milling are
required. Monitoring of the waste rocks generated
during operations is crucial for ensuring human health
safety.
Currently,
gamma-ray
spectroscopy
is
extensively used in reference to concentrations of
uranium isotopes to control radiation contamination at
uranium sites. However, gamma-ray spectroscopy
detects only gamma-emitting isotopes. In contrast,
thermoluminescence can measure the amounts of
alpha-emitting isotopes, which are detrimental to
human health. The thermoluminescence intensity can
directly determine the activity concentrations of alpha-
emitting radionuclides, and thermoluminescence can
track the activity concentration of radon daughter
products.
Thermoluminescence
has
limits
for
dating
environmental samples older than a few years; at
present, it is not used for dating them. Its primary
application lies in monitoring the conditions of interest.
Environmental thermoluminescence measurements
exhibit
advantages
over
other
methods:
thermoluminescence dating. Thermoluminescence is
basically
a
'net'
measurement:
The
thermoluminescence signal is built up in a situation in
which the environmental sample is exposed only to
natural radiation, so the measurement is a true
reflection
of
the
amount
of
alpha-emitting
radionuclides in the sample. This net measurement
property is also present in radiation environmental
thermoluminescence
measurements.
Since
the
thermoluminescence
is
rapidly
renewed,
thermoluminescence dating is likely to produce only
short-time
instability
of
the
sediment
thermoluminescence ages. A thermoluminescence age
discrepancy
is
typical
at
an
environmental
thermoluminescence monitoring area with a radical
environmental
change.
Moreover,
thermoluminescence age monotony can be checked via
thermoluminescence dating.
THERMOLUMINESCENCE IN GEOLOGY
The
first
real
geological
application
of
thermoluminescence (TL) was carried out in 1967. It
managed to measure the doses of ionizing radiation
delivered to quartz grains, and thus estimate the age of
geological materials. The favorable discovery of TL in
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geological samples, with the possibility of determining
geological ages, developed for practically all
characteristic TL bands. Moreover, it was possible to
develop TL dating by measuring very small samples of
quartz from sediments and rocks. Since the first
successful age determination of approximately 20,000
years, there have been numerous paleodose
determinations of TL in sediments and stones. TL dating
of sediments and rocks is well established as a research
tool. TL dating is used with the same ease as carbon
dating when this dating method does not reach the
desired age limits. The advantages of TL are that there
is no contamination and that there is no need for a
prerequisite to study.
These advantages are also their only limitations.
Moreover, TL is restricted to low-temperature
processes for protracted periods of time, lasting from a
few years to a few million years. TL dating is attractive
for certain types of samples from sedimentary and
volcanic areas, as well as for particular problems
ranging from early hominids to more recent dating at
the time of the last glaciation, between 100,000 years
and 10,000 years ago. Although there are several dating
methods, the most used in ages below 1 million years
are the TL dating methods. It is also the best study
option when the sample is too small for other analytical
techniques.
1. Sediment Dating
Sediment Dating: Sediments are layered sequences,
often
enriched
in
certain
compositions
in
corresponding time periods, that receive material from
pre-existent surfaces or from certain outside sources
according to specific temporal or climatic regimes.
When observed in the geological column, these layers
indicate the geochronologic history of the planet. The
sedimentation process is a physical or chemical
deposition of material that comes from certain
elevated terrains or inside the ocean basin. Sediment
dating gives information about the length of the
accumulation stage that each stratum represented, the
periodicity of the climatic changes, and the rate of
erosion of the older surfaces, which serves to modulate
the accumulation of sediments in each corresponding
time period. In the ocean or great lakes, sediments are
accumulated at a very low rate, on the order of
millimeters in thousands of years. The dating of these
older and recent materials can be done through the
dating of the sands that are in the middle of the mud
layers or in organic matters that are located in the mud
layers. The densities used for the dating of sediments
have been those of quartz or feldspar in their
compacted forms, also using their different chemical
compositions if they are not consolidated.
While quartz and feldspars are mainly used to date
sediments, TL dating has a wide use in relation to the
piers of dunes, lagoons, deltas, and sandy beaches,
since the innovations that the TL method has had, so
that they can see at greater depths and with sufficient
precision are undeniable. With TL, sediments that have
been accumulated at different times can be dated,
controlling the activity of the different inputs. The
importance of TL is that it has given new answers to old
questions about the history of accumulation of these
sediments, since the periods correspond to non-
sedimentary periods. The importance of dating these
sediments lies in finding correlations with the
development of prehistoric civilizations, climatic
changes, and short geochronological periods of
hurricanes, floods, and paleo-seismic events.
2. Rock Analysis
Max. hours of luminescence signal in rock phase are
made from TL and OSL data that enable comparison of
the TL ages with U-Pb ages for the same sample. The TL
recorded on muscovite and biotite grains has been used
to dating the Runeberg granite in Finland as Oldest
Intrusions In Fennoscandian Shield Completed By
Zircon UPb Ages. This unpublished magmatic
historiography with TL ages must be controlled with
reliability and precision. The luminescence dating of
crystalline rocks has been intensively studied on mica
grains, but the understanding of the heating impact on
the
trapping
centers
of
TL
signal
and
thermoluminescent setting was published only
recently. TL signal in heated grains was interpreted as
age distortion indicating that final thermal treatment
must be set at stable TL signal. In other cases TL signal
has been used to difference the modes of the uplift of
granite stock in Anzab Ridge in folded mode. After that
we investigated about 300 granite samples using TL
dating and apatite fission-track analysis for the Western
Caucasus. Implications are that paleotemperature
modeling based on the measurements of surfaces of
fission tracks erased partially by thermal eduction
should be provided for TL-dated granite
–
knowledge
about pre-Cenozoic thermal history of folded settings
in the Caucasus. The superficial time increase
presumably should be the way of AFT-dating in
unfaulted segments of crust.
Investigation of TL signal in quartz and feldspars by TL-
datings should be provided in different sites of same
rock massif. Aged rocks should be also investigated
with additional comparisons of a TL
–
AP and Rb-Sr ages
of granite mapping at the Same Area. But TL dating of
granite should be controlled by U
–
Pb dating of zircon
except TLS silica cement for sediments and the ages of
collision deformations of folded molasses. The
absorbed AD in quartz blocks from the belt-gray granite
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sepals had been taken to TL dating the Ruinovaya Gora
granite
–
the oldest period of high-temperature
tectonics with K-Ar dating. The TL dating of 390 Ma was
provided only for quartz samples, however the Zr
content in quartz was studied to choose samples
utilizing TL center not blinded by the high content of
Zr4+. Then age differences in this zone and the absence
of age differences shifted to the fault at 200 Ma. quartz
veins
–
Questions To Geological Consequences Of
Quartz Veins Dating, Was Conducted In About 700
Granitic Rock Samples For France With Included Quartz
Samples From The Chugoshin Goryn Superficial Area.
ADVANCEMENTS
IN
THERMOLUMINESCENCE
RESEARCH
The thermoluminescence (TL) analysis of minerals,
rocks and sediments is an important tool for
archaeologists and geologists, particularly for the age
determination of aggraded sedimentary deposits
outside the range of radiocarbon dating, where TL
dating has established itself as the standard technique.
New technological developments have led to more
sensitive and miniaturized readout equipment that
allow for applications in the field, as well as in
antiquities testing, where small sample dimensions are
essential. A wide variety of materials have been
identified as TL sensitive in the past, many of which
have not been studied extensively. In addition, new
synthetic TL phosphors are regularly developed for use
in dosimetry and other radiation and nuclear related
areas. In the context of this chapter, we will review
recent advancements in TL phosphor development for
the purpose of TL dating and luminescence dosimetry,
recent innovations in readout techniques and
instrumentation and their applications. An important
component of TL dating systems for mineral extraction
from luminescent sedimentary deposits is the
availability of suitable luminescence dating reference
materials, ideally calibrated by secondary methods for
dose and energy response. Such reference materials
are often commercial phosphors for TL dosimetry,
where costly calibration is usually the responsibility of
the commercial producer. The properties of
commercial TL phosphors used in dosimetry have been
reviewed extensively, however, little information is
available with regard to their applicability as sources for
the secondary calibration of TL dating systems. These
phosphors are predominantly LiF-based materials,
where Li impurities in the source can have a
considerable effect on the TL response and its
dependence on the low-energy component, i.e., below
1 keV, of the incident photon spectrum, an important
consideration for a dating system. Although the LiF
absorption edge lies at 12 eV, phosphors such as LiF:Cu,
- P, were observed to have significant sensitivity below
this energy.
1. New Materials
Several factors have motivated researchers to develop
new TL materials. TL dosimeters used for personal and
medical doses must have an adequate response to all
natural and artificial radiations. TL detectors used for
radiation dosimetry in physical and geological dating
need to have a TL glow curve shape, peak temperature,
and TL properties suitable for the goal. For use as a label
without modification of the fingerprint, the TL response
must remain constant over time and have the same
characteristics of a natural lack. In the case of fire
investigation, the TL response must be sufficiently high
so recovery is possible and, if necessary, the glow curve
must have the same characteristics of a natural lack of
the specific soil. In all these conditions, natural
materials present some drawbacks. TL natural signals
may vary depending on weather conditions and
radiological environment. The TL signal from natural
materials may approach the limit of detection in fire
investigation. For personal and medical dosimetry, the
TL signals of natural materials may have very low
sensitivity.
Although many TL materials have been proposed for TL
applications, very few have been widely exercised. This
is probably a consequence of the fact that, for many TL
applications, natural materials are sufficient. Here, we
present several new TL materials that exhibit
remarkable characteristics for TL applications in
biomedical, geological, and physical safety areas. For X-
ray dosimetry, the main need has been for materials
with high sensitivity but very low fading. Al2O3:C was
proposed for personal dosimetry and showed very low
fading during the first years of service. Some years after
the launch of Al2O3:C, other materials appeared, such
as LiF:Mg,Cu,P; LiF:Mg,Cu; Li2B4O7:Cu; LiF:P; Li2SiO5;
BaCl2; and CaS:Eu. These materials have very low
fading in laboratory conditions, making their use
interesting.
In the following, we present other TL materials
proposed to fill the above requirements in TL
applications. We divide the review into TL materials
used in the last few years, TL materials without
commercial applications, and materials not yet used for
TL applications, but that present properties interesting
for potential applications.
2. Innovative Techniques
During the past five decades, there has emerged a
continuous effort to elaborate new and more efficient
techniques for luminescence signal readout, dose
determination, dating, and a range of applications
involving dosimetry and dating of different materials.
With that purpose, numerous inventions have been
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described in the specialized literature. Many of these
innovations have greatly developed the art of
luminescence detection. However, most of these
reports are unpublished, lying in the confidential
records of some laboratories. Some examples of
recognizably licit and productive patents can be found.
Innovative work can frequently be found in the
“general” patents of the lumi
nescence laboratories or
companies that processed luminescence signals or
constructed luminescence devices. Many, maybe the
majority of luminescence resorts, work in the familiar
manner of inventive machines or methods of great
commercial success. A less charged description of the
subject can be found in the bibliography. This list is
compiled according to the chronological order of
publication, for any specific theme or applications.
Customarily, this innovative work has mostly involved
different aspects of luminescence readout such as
signal stimulation and detection. The main aspects of
these general advancements are briefly discussed in
the following. A major part of these advanced
techniques has broad applicability to TL as well as OSL,
non-necessitating the complex cascade of the TL signal
in almost two hundred independent detectors that
should be done in order to calibrate the TL signal of any
powder detector.
CHALLENGES AND LIMITATIONS
Thermoluminescence (TL) is an appealing and versatile
tool for both scientific research and several
technological applications. However, it also has some
important challenges and limitations that one must
consider before using it. In the following, we describe
some of the important challenges related to TL and
some of their solutions.
1. Measurement Uncertainties
Thermoluminescence is currently used in several
scientific and technological applications that can
impact people's lives in several ways, such as
archaeological dating, forensic science, blood glucose
measurement,
essential
oil
characterization,
environmental monitoring, and lithological studies. It is
well-known that, depending on the application, TL can
be measured either for qualitative or quantitative
purposes. In both situations, the quality of the TL signal
is important, since a poor-quality TL signal could lead to
wrong conclusions or TL results with very low
confidence intervals. In some applications, such as
archaeological dating, the TL data processing is so
critical that TL is the last resort method for cross-dating
the thermoluminescence signal with the optically
stimulated luminescence signal.
In these situations, the restrictions imposed by dose
rate calculation and optical bleaching must be well
considered. In contrast, during a blood glucose level
measurement, it is very important to obtain a highly
sensitive TL signal with low uncertainty values to avoid
misdiagnosis. In some of the applications listed above,
if the TL measurement is performed weekly or monthly,
the TL signal must present some degree of
reproducibility over time. In addition, the TL signal
properties must not vary between each irradiated
sample in the same TL measurement batch, otherwise,
it may lead to misleading conclusions.
2. Material Limitations
Materials can present some limitations depending on
the TL application. Some TL materials can present high
sensitivity, while another one can present a very low
sensitivity. The TL sensitization behavior of a certain
material is an important parameter to take into account
in TL applications. Although more than 200 materials
are known, high-sensitivity TL semiconductors, such as
quartz, Al2O3, and LiF, are still the most widely studied,
even if scintillators have an important mass and energy
sensitivity. Among the TL semiconductors, Al2O3
ceramics have an extremely high sensitivity and an
adequate dose range. Other TL phosphors do not have
an adequate dose range for practical TL applications.
Measurement Uncertainties
For over 50 years, thermoluminescence (TL) has offered
a wealth of valuable information about a sample,
making it a technique of considerable promise for
applications in fields such as Quaternary science,
geology, material science, archaeology and art history.
Although its ecosystem is riddled with experimental
and material challenges, TL is often marketed as a
"simple" technique to implement. Here, we discuss
several "easy to overlook" problems lurking within the
TL experimental ecosystem, which, if not recognized,
can lead to erroneous sample interpretations, as well
as competition from other dating techniques can make
TL a difficult sell. We will explain how solving these
issues can lead to a more robust age report by
leveraging recent advances in the TL experimental
environment.
The uncertainties associated with a TL measurement
will most commonly be a combination of errors
resulting from both sample analysis and age
calculation. For the analytical part of the uncertainty,
we can use the statistical errors from our experimental
analysis. Then we can add to that a measure of the
uncertainty associated with how we model the shape
of the TL curve, as well errors associated with signal
intensity loss as a function of time before
measurement, the effect of beta dose caused by
natural beta radiation from the sample material, etc.
From this, we can construct a joint distribution of errors
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from which we can then propagate the uncertainties
into the final age calculation using standard error
propagation techniques. Given the assumption of all
measurement error contributions being Gaussian, the
final thermal age will typically have a Gaussian
distribution centered around the output value of the
age calculation, along with a standard deviation
magnitude given by the width of the joint distribution,
propagated using standard rules. However, this
standard procedure does not apply universally, and is
especially likely to break down in situations
characterized by non-standard measurement error
behaviors.
Material Limitations
The second major challenge lies in the response of the
material and the relationship between radiation effects
and signal characteristics. It is well known that the
thermoluminescence glow-response from a material,
that is, the shape, location, and intensity of its glow
peaks, depends on various factors, including heating
rate, ambient light, preheat, and prior irradiation.
These diagnostic input parameters are often partly
interrelated and, thus, not really independent. It is also
clear that the signal shape must depend upon the
intrinsic properties of the material and specific defect
centers present. It is also known that the location,
depth, and nature of the electron or hole traps in the
band gap, and the locations of the luminescent
recombination centers and their respective cross-
sections for trapping, and for recombination, affect the
properties. Selection of favorable assay conditions is
crucial in order to minimize uncertainties in the results.
This is one of the major reasons for using a plurality of
specific materials or for varying the specific details
between samples of the same material.
It is known that previous problems arise in materials
with a high concentration of impurities, owing to trap
filling, that affect the signal pulses. Loosely bound
electrons and holes are detected in materials with a
high defect density. Thermoluminescence from band
bands tends to be broader than that from deep traps,
and has an intensity ratio and distribution, central
depth and luminescent color that depend mainly on the
type of deep levels and on the shape of the available
band edges. Deep shallow electron traps close to the
conduction band bottom predominantly determine
thermoluminescence in semiconductors with a high
imperfection density. Deep shallow hole traps close to
the valence band edge are observed in low
imperfection density insulators and semiconductors.
Trapping cross-sections are larger for shallow defects
than for those that are deeper in the gap.
FUTURE DIRECTIONS IN THERMOLUMINESCENCE
1. Emerging Applications
Thermoluminescence (TL) has been widely used as a
tool for thermochronometry, dating minerals
associated
with
the
initiation
of
some
geomorphological events, and measuring the
accumulated doses in materials, such as quartz and
feldspars. These typical applications are well covered
by TL dating literature, and studies related to them are
still being published, as expected by the majority of the
TL community. However, TL is now also being used in
more sophisticated and innovative systems with
emerging applications, as illustrated below. These uses
bear witness to the synergies that may arise from the
combination of the TL technique with new
technological advances in other fields, so benefiting
from a truly interdisciplinary research approach. There
is a clear trend towards miniaturization, integration and
automation of measurement systems. The availability
of low-cost, compact and miniaturized components has
led to more efficient systems, which often travel to
remote inaccessible places or places devoid of basic
infrastructure. This is particularly important in
paleoseismology, where field dating is sometimes
impossible due to the absence of optical stimulation
and/or the lack of a vacuum system.
2. Interdisciplinary Approaches
TL is often regarded as a dated technique, particularly
by young researchers seeking new technologies and
instruments. Development of systems that provide
stable, compact, affordable and easy to operate TL
detectors and stimulators capable of making more
rapid and detailed TL measurements could certainly
help keep the TL technique on the cutting edge of
research and novel applications, rather than just a
documentary format for fossils. And wait a minute:
Have researchers at the forefront of technology
actually created sensors capable of measuring
luminance so quickly? If so, and relevant patents for TL
can be purchased, would it be possible to create a TL
system with the required performance?
Emerging Applications
The venerable fields of archaeology and geology have
benefitted the most from TL dating in the last few
decades. With the continued frictional heating related
to numerous tectonic events, dating events, as well as
thermally resetting exposure ages of natural and man-
made silicate structures that may be geologically active,
has warranted the development and application of TL
to other fields of science. Paleoseismology has
confirmed the interest of the accumulated public
masses in the recurrence of earthquakes in order to
ensure their safety. To this end, TL must further more
efficiently date the sedimentary false bottoms of active
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fault traces at millennial scales. Geophysical interest in
hotspot stability forces questions and proposals for
experimental calibrations. Quasi-experimental TL
laboratories are being set up and are developing
collaborative wide-scale experimental temperature TL-
programming on different samples with the aim of
being able to test the heating event temperature and
duration.
The human fascination with the geo-archaeological
knowledge of their region has led them to further
explore their environment. Accumulated urban
collapses near pedogenic seismic markers are consoling
to understand the stability of a city and its importance.
TL is regularly called upon to respond to the forensic
demands of various upheavals, allowing for the design
of TL databases by different investigation groups. These
databases will serve to refine TL parameters, help study
specific cases, and generate TL response maps for
practical forensic tools.
Interdisciplinary Approaches
In recent years, a wealth of cross-disciplinary research
has appeared, taking advantage of the various
physicochemical
properties
of
materials
that
luminesce. For example, confinement may modulate
the properties of nanocrystalline TL phosphors
embedded in a polymer matrix. This and similar ideas
took advantage of scintillating, and even TL materials,
which have potential applications in gamma-ray
detection as these scale down to the personal
protective measures. Dense ceramic TL materials may
also find application in scintillators or photo-detectors
to remote detect events of interest or detect
counterfeit archives for carbon dating. In this turn,
ceramic TL phosphors exhibit greater insulation against
χ
-ray damage than their dense counterparts, thus
opening a new avenue into developing devices capable
of running for extended periods in radiation-prone
areas.
Work and collaboration with the astrophysics
community relying on nucleon-nucleon collision
experiments guided the design of novel sensing and TL
prototypes opening a more recent frontier in TL by
moving the initial device concept from an atomic-scale,
hypersensitive remotely-reading ensemble of devices
back to micro and nanoscale, self-sensing devices. The
heavier the TL centers the higher the absorption, the
device resistivity is lowered when self-sensing under a
putting photon flux such as that from radioactive
decays, which can be used for artificial-label device
taggings. Counting requires no shielding or active
electronic reading, coherent data can be transferred
over very long-distance, all-device design, resources,
mode of operation, and device function externally. The
challenge is now on going back to atomic scale,
hypersensitive, outstandingly controlled material
processing, and TL host doping at LPA flux, using down-
scaling at sub-wavelength cost-effective optics again.
CONCLUSION
This is the twelfth section the book
In this chapter, we have reviewed the principles and
techniques of TL, with special emphasis on its
application in dosimetry. In the first section of the
chapter,
the
underlying
principles
of
thermoluminescent phosphor materials have been
summarized, including their electron trap energy levels,
charge transport, design properties, and the radiative
recombination process. We have briefly described
some aspects of the materials preparation and
characterization, not only of TL materials but also of
those competing with TL for dosimetric applications.
The TL exposure metrology is outlined, with a special
emphasis on TL glow curves. Subsequently, we have
summarized TL applications in the areas of personnel
and environment monitoring, accident dosimetry, and
of other fields that range from geology to paleontology,
space radiation and semiconductor technology, with
focus on key applications and recent developments in
each area. The last two sections concern applications of
optically
stimulated
luminescence,
which
we
designated the twin sister of TL, besides a brief
selection of selected OSL applications. The TL and OSL
techniques have many aspects in common, including
the underlying physical principles, the need for careful
preparation of the phosphors, exposure and reader
systems, the deconvolution of the TL glow curves and
OSL decay curves. Therefore, it is useful to introduce
OSL applications for comparison and complementarity
purposes.
Thermoluminescence materials are prepared from
oxides and some fluorides, doped with impurities or
native defects. The preparation conditions deeply
affect
the
crystallization,
microstructure
and
optoelectronic
properties
of
the
materials.
Additionally, engineering the fabrication parameters
will provide for luminescences that fit specific
applications. Thorium-doped aluminum oxides are a
key TL compound used for personnel and
environmental radiation monitoring due to their
reliable TL properties, namely that the glow curve has a
peak and is stable with time. The TL response of these
and of some other key TL materials used for emergency
and accident dosimetry shows some other traits, which
are not an inherent trait of TL, but come from the
thermal treatment, purification and annealing of the
emitted radiation on added impurities.
REFERENCE
European International Journal of Multidisciplinary Research
and Management Studies
22
https://eipublication.com/index.php/eijmrms
European International Journal of Multidisciplinary Research and Management Studies
Chen, R., & McKeever, S. W. (1997). Theory of
thermoluminescence and related phenomena. World
Scientific.
