P. Sahare | University of Delhi (original) (raw)

Papers by P. Sahare

Radiation protection dosimetry, 2015

This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca... more This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors for different doses and bleaching durations. The results have also been compared with the commercially available Landauer Al2O3:C (Luxel®) dosemeter. Nanocrystalline K2Ca2(SO4)3:Eu is known to be a sensitive thermoluminescent phosphor, but its OSL response is hardly reported. At first, pellets of nanocrystalline K2Ca2(SO4)3:Eu powder were prepared by adding Teflon as a binder. Their OSL signal was compared with that of the material in pure form, i.e. without adding the binder (in 100:1 ratio). It was observed that adding the binder does not appreciably affect the OSL intensity. On comparison with the commercially available Al2O3:C from Landauer, it was found that K2Ca2(SO4)3:Eu is around 15 times less sensitive than Al2O3:C. 'Homemade' BaFCl:Eu phosphor has also been studied. The intensity of BaFCl:Eu was ∼20 times more than the standard Al2O3:C dosemeter and...

Nanocrystalline samples of Mn-doped CaF2 were synthesized by chemical coprecipitation method. The... more Nanocrystalline samples of Mn-doped CaF2 were synthesized by chemical coprecipitation method. The
impurity concentration was varied in the range of 0.5e4.0 mol%. The structure of the synthesized material
was confirmed using powder XRD analysis. TEM images of the nanoparticles show their size
occurring mostly in the range of 35e40 nm, with clusters of some impurity phases formed on annealing
of the material at higher temperatures. Detailed studies on TL showed that the structures of glow curves
depend on Mn concentrations and annealing temperatures. Optimization of the concentration and
annealing temperature showed that the sample (doped with 3.0 mol% and annealed at 673 K) has almost
a single dosimetric glow peak appearing at around 492 K. EPR and PL spectra were further studied to
understand the reasons for changes in the glow curve structures. All detailed studies on TL, PL and EPR
showed that the changes in glow curve structures are caused not only by the stress connected with the
difference in ionic radii of host Ca2þ and the guest impurity Mn3þ/Mn2þ, but are also governed by other
reasons, like diffusion of atmospheric oxygen and formation of impurity aggregates, such as, MnO2,
Mn3O4, etc. This is true not only for nanocrystalline CaF2:Mn but could also be so for the bulk CaF2:Mn
(TLD-400) and would thus help in understanding complex glow curve structure, high fading and the loss
of reusability on annealing beyond 673 K.

Journal of Luminescence, 2010

Nanocrystalline LiF:Mg,Cu,P phosphor material of different shapes and sizes (microcrystalline cub... more Nanocrystalline LiF:Mg,Cu,P phosphor material of different shapes and sizes (microcrystalline cubic shape, nanorod shape and nanocrystalline cubical shaped) have been prepared by the chemical co-precipitation method. Thermoluminescence (TL) and other dosimetric characteristics of the phosphor are studied and presented here. The formation of the materials was confirmed by the X-ray diffraction (XRD). Its shapes and sizes were also observed using

Physica Status Solidi (a), 2007

Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low-Zeff, tissue-equivalent material th... more Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low-Zeff, tissue-equivalent material that is commonly used for medical dosimetry of ionizing radiations such as gamma and X-rays using the thermoluminescence (TL) technique. Nanocrystals of the same material are produced and their TL characteristics are studied. It is found that the nanocrystalline MgB4O7:Dy with a dopant concentration of 1000 ppm is the most sensitive amongst varying dopant concentrations, with its sensitivity equal to 0.025 times that of the standard phosphor CaSO4:Dy. The glow curve has two peaks at 154 °C and 221 °C. The nanophosphor has very poor sensitivity for low doses up to 10 Gy but beyond this dose the phosphor exhibits a linear response up to 5000 Gy. On increasing the dose further the response first becomes supralinear and then sublinear, finally resulting into saturation. Considering also its low fading particularly under post-irradiation annealing and excellent reusability features, this nanophosphor may be used for high dose (10–5000 Gy) measurements of ionizing radiations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ce3?-doped NaLi2PO4 orthophosphate (with different impurity concentrations, i.e., 0.01–0.3 mol%) ... more Ce3?-doped NaLi2PO4 orthophosphate (with
different impurity concentrations, i.e., 0.01–0.3 mol%) was
prepared by a solid state reaction method. Formation of the
material was confirmed using powder X-ray diffraction
analysis. TL intensity was found to be the highest for the
material having impurity concentration 0.2 mol% after
annealing it at around 600 K for 1 h and subsequently
quenching to room temperature. A typical glow curve
consists of three peaks at around 454, 493 and 570 K
(dosimetry peak). Good sensitivity (*8 times more than
that of TLD-100), low fading (*15 % in 2 months), low-Z
material (Zeff & 10.8), very wide dose response (i.e.,
0.1 Gy–1.0 kGy of c rays) make the material a ‘good’
thermoluminescent dosimeter (TLD) phosphor suitable for
personnel, medical and environmental dosimetry of highenergy
radiation using TL. It could also be used during
cancer therapy and sterilization of food where high doses
are needed to be monitored.

A new highly sensitive, low-Z (Zeff z 10.8) TLD phosphor, Eu3þ doped NaLi2PO4, was successfully s... more A new highly sensitive, low-Z (Zeff z 10.8) TLD phosphor, Eu3þ doped NaLi2PO4, was successfully synthesized
via solid state diffusion method. The formation of the single phase compound was confirmed by
Powder X-Ray diffraction (PXRD) analysis. Variation of the doping level has shown that the impurity
(Eu3þ) concentration for maximum TL sensitivity is 0.5 mol%. Heat treatments given to achieve the high
TL sensitivity of this phosphor also showed that it needs to be annealed at 973 K for 1 h. Incorporation of
the impurity in the Euþ3 states was confirmed by the PL emission peaks. The TL glow curve consists of a
prominent dosimetry peak at around 458 K besides small shoulders on both sides at around 400 and
500 K. The dose response of the phosphor was found to be sub-linear up to 10 Gy of the dose and later it
becomes linear till it start saturating beyond 1 kGy. The TL sensitivity of the newly developed
NaLi2PO4:Eu3þ phosphor to g radiation from 137Cs (in the linear dose range) was compared to some
standard commercially available phosphors, such as, TLD-100, TLD-400, TLD-700H and TLD-900. It was
found to be much more sensitive than these phosphors except TLD-700H, which is w2 times more
sensitive. Easy method of synthesis, simple glow curve structure, high sensitivity, low fading, wide range
of doses and very good reusability make the phosphor a suitable candidate for the TL dosimetry.

Journal of Physics D: Applied Physics, 2005

Highly sensitive K2Ca2(SO4)3 : Eu thermoluminescence detector phosphor was irradiated at room tem... more Highly sensitive K2Ca2(SO4)3 : Eu thermoluminescence detector phosphor was irradiated at room temperature by 7Li ion beams at 24 and 48 MeV for different ion fluences in the range 109-1012 ions/cm2 using a 16 MV Tandem Van de Graff Type Electrostatic Pelletron Accelerator at the Nuclear Science Centre, New Delhi, India. The samples from the same batch were also irradiated

Radiation Effects and …, 2004

K2Ca2 (SO4) 3 microcrystalline pure, doped with Eu, Tb and co-doped with Eu, Tb was prepared by s... more K2Ca2 (SO4) 3 microcrystalline pure, doped with Eu, Tb and co-doped with Eu, Tb was prepared by solid-state diffusion method. Nanoparticles of these phosphors were also prepared by the chemical co-precipitation method. The formation of the compounds was ...

Eu3? doped NaLi2PO4 red luminescent phosphor has been synthesized by solid state reaction and its... more Eu3? doped NaLi2PO4 red luminescent phosphor has been synthesized by solid state reaction and its phase
purity has been confirmed by X-ray diffraction analysis. Optical properties of the phosphor have been investigated and the
effect of dopant (Eu3?) concentration (0.1–3.0 mol%) has been observed. Excitation spectra of the phosphor NaLi2-
PO4:Eu3? show a very efficient absorbance band corresponding to the common allowed transition 7F0 ? 5L6 occurring at
393 nm, while the luminescence spectra exhibit prominent emission peak centered at 702 nm (5D0 ? 7F4) in pure red
region. Color purity of this red phosphor has been calculated and found to be around 99.9 %, which is very close to that of
commercial red phosphor Y2O3:Eu3?. Luminescence studies of the phosphor show excellent stability with respect to
excitation energy. Chromatic investigations have also been performed using emission spectrum and some important
chromatic parameters are calculated using CIE-1931 color calculator in order to find potential application of the phosphor.

Radiation protection dosimetry, 2015

This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca... more This paper investigates the optically stimulated luminescence (OSL) response of BaFCl:Eu and K2Ca2(SO4)3:Eu phosphors for different doses and bleaching durations. The results have also been compared with the commercially available Landauer Al2O3:C (Luxel®) dosemeter. Nanocrystalline K2Ca2(SO4)3:Eu is known to be a sensitive thermoluminescent phosphor, but its OSL response is hardly reported. At first, pellets of nanocrystalline K2Ca2(SO4)3:Eu powder were prepared by adding Teflon as a binder. Their OSL signal was compared with that of the material in pure form, i.e. without adding the binder (in 100:1 ratio). It was observed that adding the binder does not appreciably affect the OSL intensity. On comparison with the commercially available Al2O3:C from Landauer, it was found that K2Ca2(SO4)3:Eu is around 15 times less sensitive than Al2O3:C. 'Homemade' BaFCl:Eu phosphor has also been studied. The intensity of BaFCl:Eu was ∼20 times more than the standard Al2O3:C dosemeter and...

Nanocrystalline samples of Mn-doped CaF2 were synthesized by chemical coprecipitation method. The... more Nanocrystalline samples of Mn-doped CaF2 were synthesized by chemical coprecipitation method. The
impurity concentration was varied in the range of 0.5e4.0 mol%. The structure of the synthesized material
was confirmed using powder XRD analysis. TEM images of the nanoparticles show their size
occurring mostly in the range of 35e40 nm, with clusters of some impurity phases formed on annealing
of the material at higher temperatures. Detailed studies on TL showed that the structures of glow curves
depend on Mn concentrations and annealing temperatures. Optimization of the concentration and
annealing temperature showed that the sample (doped with 3.0 mol% and annealed at 673 K) has almost
a single dosimetric glow peak appearing at around 492 K. EPR and PL spectra were further studied to
understand the reasons for changes in the glow curve structures. All detailed studies on TL, PL and EPR
showed that the changes in glow curve structures are caused not only by the stress connected with the
difference in ionic radii of host Ca2þ and the guest impurity Mn3þ/Mn2þ, but are also governed by other
reasons, like diffusion of atmospheric oxygen and formation of impurity aggregates, such as, MnO2,
Mn3O4, etc. This is true not only for nanocrystalline CaF2:Mn but could also be so for the bulk CaF2:Mn
(TLD-400) and would thus help in understanding complex glow curve structure, high fading and the loss
of reusability on annealing beyond 673 K.

Journal of Luminescence, 2010

Nanocrystalline LiF:Mg,Cu,P phosphor material of different shapes and sizes (microcrystalline cub... more Nanocrystalline LiF:Mg,Cu,P phosphor material of different shapes and sizes (microcrystalline cubic shape, nanorod shape and nanocrystalline cubical shaped) have been prepared by the chemical co-precipitation method. Thermoluminescence (TL) and other dosimetric characteristics of the phosphor are studied and presented here. The formation of the materials was confirmed by the X-ray diffraction (XRD). Its shapes and sizes were also observed using

Physica Status Solidi (a), 2007

Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low-Zeff, tissue-equivalent material th... more Magnesium borate activated by dysprosium (MgB4O7:Dy) is a low-Zeff, tissue-equivalent material that is commonly used for medical dosimetry of ionizing radiations such as gamma and X-rays using the thermoluminescence (TL) technique. Nanocrystals of the same material are produced and their TL characteristics are studied. It is found that the nanocrystalline MgB4O7:Dy with a dopant concentration of 1000 ppm is the most sensitive amongst varying dopant concentrations, with its sensitivity equal to 0.025 times that of the standard phosphor CaSO4:Dy. The glow curve has two peaks at 154 °C and 221 °C. The nanophosphor has very poor sensitivity for low doses up to 10 Gy but beyond this dose the phosphor exhibits a linear response up to 5000 Gy. On increasing the dose further the response first becomes supralinear and then sublinear, finally resulting into saturation. Considering also its low fading particularly under post-irradiation annealing and excellent reusability features, this nanophosphor may be used for high dose (10–5000 Gy) measurements of ionizing radiations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ce3?-doped NaLi2PO4 orthophosphate (with different impurity concentrations, i.e., 0.01–0.3 mol%) ... more Ce3?-doped NaLi2PO4 orthophosphate (with
different impurity concentrations, i.e., 0.01–0.3 mol%) was
prepared by a solid state reaction method. Formation of the
material was confirmed using powder X-ray diffraction
analysis. TL intensity was found to be the highest for the
material having impurity concentration 0.2 mol% after
annealing it at around 600 K for 1 h and subsequently
quenching to room temperature. A typical glow curve
consists of three peaks at around 454, 493 and 570 K
(dosimetry peak). Good sensitivity (*8 times more than
that of TLD-100), low fading (*15 % in 2 months), low-Z
material (Zeff & 10.8), very wide dose response (i.e.,
0.1 Gy–1.0 kGy of c rays) make the material a ‘good’
thermoluminescent dosimeter (TLD) phosphor suitable for
personnel, medical and environmental dosimetry of highenergy
radiation using TL. It could also be used during
cancer therapy and sterilization of food where high doses
are needed to be monitored.

A new highly sensitive, low-Z (Zeff z 10.8) TLD phosphor, Eu3þ doped NaLi2PO4, was successfully s... more A new highly sensitive, low-Z (Zeff z 10.8) TLD phosphor, Eu3þ doped NaLi2PO4, was successfully synthesized
via solid state diffusion method. The formation of the single phase compound was confirmed by
Powder X-Ray diffraction (PXRD) analysis. Variation of the doping level has shown that the impurity
(Eu3þ) concentration for maximum TL sensitivity is 0.5 mol%. Heat treatments given to achieve the high
TL sensitivity of this phosphor also showed that it needs to be annealed at 973 K for 1 h. Incorporation of
the impurity in the Euþ3 states was confirmed by the PL emission peaks. The TL glow curve consists of a
prominent dosimetry peak at around 458 K besides small shoulders on both sides at around 400 and
500 K. The dose response of the phosphor was found to be sub-linear up to 10 Gy of the dose and later it
becomes linear till it start saturating beyond 1 kGy. The TL sensitivity of the newly developed
NaLi2PO4:Eu3þ phosphor to g radiation from 137Cs (in the linear dose range) was compared to some
standard commercially available phosphors, such as, TLD-100, TLD-400, TLD-700H and TLD-900. It was
found to be much more sensitive than these phosphors except TLD-700H, which is w2 times more
sensitive. Easy method of synthesis, simple glow curve structure, high sensitivity, low fading, wide range
of doses and very good reusability make the phosphor a suitable candidate for the TL dosimetry.

Journal of Physics D: Applied Physics, 2005

Highly sensitive K2Ca2(SO4)3 : Eu thermoluminescence detector phosphor was irradiated at room tem... more Highly sensitive K2Ca2(SO4)3 : Eu thermoluminescence detector phosphor was irradiated at room temperature by 7Li ion beams at 24 and 48 MeV for different ion fluences in the range 109-1012 ions/cm2 using a 16 MV Tandem Van de Graff Type Electrostatic Pelletron Accelerator at the Nuclear Science Centre, New Delhi, India. The samples from the same batch were also irradiated

Radiation Effects and …, 2004

K2Ca2 (SO4) 3 microcrystalline pure, doped with Eu, Tb and co-doped with Eu, Tb was prepared by s... more K2Ca2 (SO4) 3 microcrystalline pure, doped with Eu, Tb and co-doped with Eu, Tb was prepared by solid-state diffusion method. Nanoparticles of these phosphors were also prepared by the chemical co-precipitation method. The formation of the compounds was ...

Eu3? doped NaLi2PO4 red luminescent phosphor has been synthesized by solid state reaction and its... more Eu3? doped NaLi2PO4 red luminescent phosphor has been synthesized by solid state reaction and its phase
purity has been confirmed by X-ray diffraction analysis. Optical properties of the phosphor have been investigated and the
effect of dopant (Eu3?) concentration (0.1–3.0 mol%) has been observed. Excitation spectra of the phosphor NaLi2-
PO4:Eu3? show a very efficient absorbance band corresponding to the common allowed transition 7F0 ? 5L6 occurring at
393 nm, while the luminescence spectra exhibit prominent emission peak centered at 702 nm (5D0 ? 7F4) in pure red
region. Color purity of this red phosphor has been calculated and found to be around 99.9 %, which is very close to that of
commercial red phosphor Y2O3:Eu3?. Luminescence studies of the phosphor show excellent stability with respect to
excitation energy. Chromatic investigations have also been performed using emission spectrum and some important
chromatic parameters are calculated using CIE-1931 color calculator in order to find potential application of the phosphor.