Thermoluminescence studies of CaSO4: Eu nanophosphor for electron dosimetry

Sample of CaSO4: Eu nanophosphor has been synthesized by chemical co-precipitation method and irradiated with 6.5 MeV electrons over the fluence range from 5×1014 to 4×1015 e/cm2. The as-synthesized sample has been characterized by the XRD and TEM. The TEM image reveals that the nanocrystallites are in the form of nanorods of length 75 to 125 nm, with varying diameter of 10 to 20 nm. The XRD yields an average grain size ~15 nm, with hexagonal structure. The electron irradiated samples exhibit the thermoluminescence glow curve with a single peak at 162 °C. Moreover, the TL peak intensity increases with the increase in electron fluence and saturates beyond 3×1015 e/cm2. Moreover, TL glow curves have been theoretically fitted using computerized glow curve deconvolution (CGCD) method to determine trapping parameters. The results indicate that CaSO4: Eu can be used as a dosimeter for 6.5 MeV electrons over dose range from 15-80 kGy

Thermoluminescence, photoluminescence and optically stimulated luminescence characteristics of CaSO4:Eu phosphor: experimental and density functional theory (DFT) investigations

The CaSO4:Eu phosphor in nanocrystalline form was obtained by chemical method. The sample was annealed at various temperatures and quenched. The structural, electronic and optical properties are studied using various experimental techniques. As synthesized CaSO4:Eu particles have nanorod shapes with diameter of ~15 nm and length of ~250 nm. After annealing (at around 900 °C) a significant increase in their size (~2–4 μm) with phase transformation from hexagonal to orthorhombic was observed. Thermoluminescence (TL) and optically stimulated luminescence (OSL) intensities were found to increase with temperature up to 900 °C and decrease thereafter for 1 Gy of test dose of β-rays from 90Sr-90Yr source. However, the maximum OSL sensitivity was found to be more than that of CaSO4:Eu microcrystalline phosphor (prepared by acid recrystallization method) contrary to the usually found in the literature but much less than that of commercially available α-Al2O3:C phosphor. The activation energy for thermally assisted OSL process was found to be 0.0572 ± 0.0028 eV. The dose ranges of TL and OSL response was found from 0.04 Gy to 100 Gy and 0.02 Gy–100 Gy, respectively. The experimental results are also correlated with computational calculations based on density functional theory (DFT). The crystal structures and electronic structures of both hexagonal and orthorhombic CaSO4 and CaSO4:Eu materials show that they are direct band gap (5.67–5.86 eV) insulators, with Ca2+ substitution by Eu2+ found to introduce donor states in the band gap near Fermi level and the valence band edge of CaSO4 on doping with Eu2+ impurity ions

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-US">Thermoluminescence and photoluminescence properties of K₂Ca₂(SO₄)₃:Cu nanophosphor for gamma radiation dosimetry</span>

859-862Nanocrytstalline K2Ca2(SO4)3:Cu was synthesized by chemical co-precipitation method and annealed at 400°C. These nanocrytstalline samples were irradiated with gamma radiation for the dose varying from 500 Gy to 2000 Gy. The pre and post irradiated samples were characterized by the techniques such as XRD, SEM, UV, FTIR, photoluminescence (PL) and thermoluminescence (TL). XRD spectra show the orthorhombic structure and the crystallite size ~ 25 nm. The same is also confirmed in SEM, where the size of nanoparticles was varied from 20 to 40 nm and also shows monodispersed. Formation of the compound was also checked by FTIR, where the S-O stretching and bending mode have been observed. Whereas, in case of UV visible spectra, the band gap observed to be marginally decreased with gamma dose. In PL spectra, the emission bands are observed at 403 and 419 nm, respectively and their respective intensity increases linearly with the increase in gamma dose. In TL spectra, two dosimetric peaks have been observed at 144<span style="font-family:Symbol;mso-ascii-font-family: " times="" new="" roman";mso-hansi-font-family:"times="" roman";mso-char-type:symbol;="" mso-symbol-font-family:symbol"="" lang="EN-GB">°C and 287°C, respectively and their intensity tends to be increased with gamma radiation dose. This particular aspect shows the wide range linear TL response to the high gamma dose. Moreover, a significant shift in the peak towards lower temperature has been observed. This indicates the disorganization of the initial energy bands in the nanophosphor. In conclusion, the K2Ca2(SO4)3:Cu nanophosphor is useful for high dose gamma ray dosimetry. </span

Thermoluminescence studies of CaSO₄: Eu nanophosphor for electron dosimetry

413-419Sample of CaSO4: Eu nanophosphor has been synthesized by chemical co-precipitation method and irradiated with 6.5 MeV electrons over the fluence range from 5×1014 to 4×1015 e/cm2. The as-synthesized sample has been characterized by the XRD and TEM. The TEM image reveals that the nanocrystallites are in the form of nanorods of length 75 to 125 nm, with varying diameter of 10 to 20 nm. The XRD yields an average grain size ~15 nm, with hexagonal structure. The electron irradiated samples exhibit the thermoluminescence glow curve with a single peak at 162 °C. Moreover, the TL peak intensity increases with the increase in electron fluence and saturates beyond 3×1015 e/cm2. Moreover, TL glow curves have been theoretically fitted using computerized glow curve deconvolution (CGCD) method to determine trapping parameters. The results indicate that CaSO4: Eu can be used as a dosimeter for 6.5 MeV electrons over dose range from 15-80 kGy

Characteristics of K2Ca2(SO4)3:Eu TLD nanophosphor for its applications in electron and gamma rays dosimetry

Nanorods (~25 nm × 200 nm) of K2Ca2(SO4)3:Eu phosphor (powder) were synthesized by chemical coprecipitation method followed by annealing at 700 °C. Dimensions of nanorods were confirmed by TEM and XRD. The material (pellets) was irradiated by 60Co gamma rays for various doses over the range of 0.1 Gy–100 kGy and also by 6 MeV electrons at different fluences varying from 2.5 × 1011 e/cm2 to 5 × 1013 e/cm2 at room temperature. Thermoluminescence (TL) and photoluminescence (PL) of the gamma and electron irradiated phosphors were also studied. TL glow curve apparently exhibited a peak at around 152 °C with a small hump around 258 °C. The exact number of peaks in a glow curve were determined by thermal cleaning method and glow curves were further deconvoluted by CGCD method to determine trapping parameters. PL emission spectrum consisted of a single emission band at 388 nm (Eu2+ emission) on excitation by 320 nm. The intensity of this peak increased with the electron fluence up to 5 × 1012 e/cm2 and decreases thereafter. The TL response is linear in the dose range from 0.1 Gy to 1 kGy of gamma radiation and electron fluence range from 2.5 × 1011 e/cm2 to 2.5 × 1012 e/cm2. The electronic structures of the pristine and Eu doped K2Ca2(SO4)3 materials were analyzed by means of first-principles density functional theory (DFT) calculations. The dosimetric characteristics suggest that the K2Ca2(SO4)3:Eu nanophosphor can be useful for its applications in radiation dosimetry, especially, for measurement of high-doses of gamma and electrons