Phosphors are materials useful for TL Dosimeters. SK Omanwar made a major contribution to this Paper presented at Nanoscience Conference held in Lucknow University on 21-23 Dec. 2013.

1. Synthesis and Characterization of
Phosphors for TL Dosimetry
H.S. Virk1 and S.K. Omanwar2
1Department of Nanotechnology, SGGS World
University, Fatehgarh Sahib (Pb.)-140406
2Department of Physics, SGB Amravati University,
Amravati (MS) 444602

2. TL Dosimetry
• TL dosimetry is used in many scientific and
applied fields such as radiation protection,
radiotherapy, industry, and environmental and
space research, using many different materials
known as phosphors. The basic demands of a
thermoluminescent dosimeter (TLD) are good
reproducibility, low hygroscopicity, and high
sensitivity for very low dose measurements and
good response at high doses in radiotherapy and
in mixed radiation fields.

3. TLD Phosphors
• A phosphor is a substance that exhibits
the phenomenon of luminescence. Phosphors are
often transition metal compounds or rare
earth compounds of various types. The most common
uses of phosphors are in CRT displays and fluorescent
lights. Phosphors are usually made from a suitable host
material with an added activator. The host materials
are typically oxides, nitrides and oxy-
nitrides, sulfides, selenides, halides or silicates of zinc,
cadmium, manganese, aluminium, silicon, or
various rare earth metals. The activators prolong the
emission time (afterglow).

4. CaSO4: Dy Phosphor
• CaSO4 is one of the most sensitive TLD products
used in dosimetry. CaSO4: Dy and CaSO4: Tm are
the most interesting phosphors in CaSO4 series,
since their response is considerably stable. The
CaSO4: Dy phosphor has been used as a
dosimeter in radiation dosimetry particularly for
low-dose measurements. Considerable work has
been done on CaSO4 singly doped phosphors in
the last few decades, and Dy or Tm doped CaSO4
thermoluminescent phosphors are highly
attractive due to their desired dosimetric
properties.

5. Precipitation Method used for the
Synthesis of CaSO4: Dy
• Ingle et al. (Nagpur) have described the simplest
method for preparing CaSO4: Dy phosphor by
precipitation from aqueous solution of CaCl2 with
dilute sulphuric acid. For incorporating Dy,
appropriate amount of aqueous solution of DyCl3
was added prior to precipitation. Ratio of
Ca2+:Dy3+ in solution was 1000:1. The precipitate
was repeatedly washed by distilled water to
remove the traces of acid, dried and then
annealed at 975 K for 1 h followed by quenching
to room temperature (RT). This sample will be
designated as CaSO4: Dy–P.

6. Thermoluminescence glow curves of
CaSO4:Dy phosphors

7. Typical PL of Dy3+ in CaSO4:Dy

8. TL glow curve of gamma irradiated
CaSO4:Dy

9. Dose response of CaSO4: Dy as a
function of gamma absorbed dose

10. Heating Rate Effect
• CaSO4:Dy phosphor obtained was annealed at
different temperatures in the range of 773 to
1173 K for 1 h. The samples remained 24 h in the
oven and then switched off in order to reach the
room temperature. The glow curve of sensitized
CaSO4: Dy samples by giving different heat
treatments, in the temperature range (773–
1173 K), and irradiated at the gamma dose
(0.1 Gy), is recorded. It is observed that the
intensity of TL glow curve increases with
temperature.

11. TL intensity of CaSO4: Dy as a function
of annealing temperature

12. LiF: MCP Phosphor
• LiF: MCP material is being considered to be a
standard detector in TL dosimetry. LiF: MCP is
highly sensitive thermoluminescence detector, as
it is able to measure doses over a wide range
(generally from µGy to kGy). LiF:Mg,Ti was one of
the sensitive LiF based phosphor used in
personnel dosimetry. It was made commercially
available by Harshaw chemical company in 1967
(US Patent). Various laboratories developed LiF:
MCP phosphor with different dopants.

13. LiF: MCP Synthesis
• 5ml of Hydrofluoric acid (HF) was taken in a Teflon
beaker. Lithium carbonate was added smoothly to it to
form LiF. The precipitate so formed has been dried
under blowing air. To the dried precipitate, CuCl2
solution was sprinkled and dried again. This precipitate
was then heated in a test tube at 500°C with NH4Cl to
remove OH- ion traces in LiF. Reactive Atmosphere
Process was used in which powder was then poured in
graphite crucible containing MgF2 and NH4H2PO4. MgF2
is prepared freshly by adding the MgCO3 in the HF.
Crucible was heated at 870°C to melt LiF powder.
Finally melted LiF: MCP is rapidly quenched to room
temperature.

14. TL glow curve of LiF: MCP compared
with commercially available phosphors

15. Effect of Dopant Concentration
• The glow curve structure and TL intensity of LiF:
MCP is mainly dependent on the impurities
doped in the host. In order to obtain maximum TL
output from LiF: MCP, concentration of Mg, Cu
and P must be properly adjusted. Slight variation
in this can alter the dosimetric properties of the
phosphor. We varied the concentration of these
dopants as follows: Mg from (0.15% to 0.3%), Cu
from (20 ppm to 500ppm) and P from (0.6% to
2%). The concentrations mentioned here are the
concentrations of MgF2, CuCl2 and NH4H2PO4
added to LiF powder.

16. Effect of Mg concentration on TL
intensity of LiF:Mg,Cu,P Phosphor

17. Effect of P concentration on the TL
Intensity of LiF:MCP Phosphor

18. TL Emission Spectra of LiF: MCP
Phosphor prepared by RAP technique

19. Grain Size Effect on the TL of LiF: MCP

20. Effect of annealing temperature on the
TL of LiF: MCP phosphor

21. Linearity of Dose Response of LiF: MCP

22. Photon Energy Response of LiF: MCP

23. The Heating rate Effect on LiF: MCP

24. Reproducibility of LiF: MCP samples
with same Sensitivity
• In order to check the reproducibility of
samples with same sensitivity, a batch of 10
samples each of 10g weight was prepared.
Variation in the TL intensity of sample in the
batch was found to be around + 5% to – 5%.
The TL intensity of each of the sample is
around 30 % of LiF: MCP TLD-100H obtained
from Harshaw chemical company. No fading
was observed in the LiF: MCP sample
prepared by us over a period of 15 days.

25. Reproducibility of LiF: MCP

26. LiCaAlF6:Eu Phosphor
• The scintillation properties of LiCaAlF6:Eu
scintillator and its capability for thermal neutron
imaging application has been investigated.
LiCaAlF6 rare-earth-ion-doped scintillators of
neutron detectors with high efficiency have been
developed for the neutron gamma discrimination
by using the pulse shape discrimination in the
LiCAF:Ce scintillator, which is frequently used in
organic liquid scintillators, to selectively detect
neutrons with the LiCAF: Ce scintillator under an
intense high-energy gamma-ray field.

27. TL excitation and emission peaks of
LiCaAlF6:Eu(0.1%)

28. Variation in TL intensity of LiCaAlF6: Eu
with quenching temperature

29. TL emission spectra of the LiCaAlF6:Eu

30. Effect of Eu concentration on PL and TL
of LiCaAlF6: Eu Phosphor

31. Dose Response and Linearity for
LiCaAlF6: Eu and CaSO4: Dy

32. Comparison of TL glow curves of some
Commericial Phosphors

33. Energy dependence of LiCaAlF6:Eu
(0.1%) material

34. Effect of storage on the TL of LiCaAlF6:
Eu (0.1%)

35. Conclusions
• In the last three decades, consecutive studies on
CaSO4 and LiF standard materials gives a special
attendance to their use in TL and TL related
phenomena. Because of good chemical stability
and applications, above said phosphors are
prominently and consistently used in research as
well as in applied sciences. The LiF: MCP and
LiCaAlF6: Eu samples developed by our group
show a comparable TL intensity with LiF:MCP
TLD-100H obtained from Harshaw chemical
company and other commercial phosphors.