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

Abstract

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 temperatureup to 900 °C and decrease thereafter for 1 Gy of test dose of -rays from 90 Sr-90 Yr 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 to 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 bandgap (5.67−5.86 eV) insulators, with Ca 2+

Synthesis and characterization of high‐sensitivity Dy,Eu co‐doped CaSO4 thermoluminescent phosphor using coprecipitation technique

“…However, the TL glow curve of CaSO 4 :Mn exhibited a fading of 75% from its initial value after 28 days [11]. Utilizing the precipitation technique, calcium sulfate (CaSO 4 ) samples doped with terbium (Tb) and europium (Eu) were effectively synthesized [12]. The resulting phosphor exhibited dependable dosimetric properties including reproducibility, linearity, and a minimum detectable dose (MDD) on the magnitude of milligrays (mGy), which is considered an acceptable level for environmental and personal dosimetry.…”

Tunable Luminescence Properties and Elucidating the Electronic Structures of Single-Phase Spherical BaWO4: Dy3+, Tm3+, Eu3+ Phosphors for Warm-White-Lighting

“…The doping of RE ions will have an impact on the electronic structures of materials. The type and amount of doping elements can adjust the band gap and electronic state density distribution of materials, which will affect the practical application of materials [25,26]. Carvalho et al employed the Density Functional Theory (DFT) to calculate band gap, electron density of states and optical properties of the AWO 4 (A = Ca, Sr or Ba) with scheelite-type structure [27].…”

Optically stimulated luminescence decay and dosimetric properties of cerium‐doped potassium sulfate phosphor

“…[3] The all-optical nature of the OSL method indicated its advantage over TL and has caused increased interest in OSL for dosimetric applications. Calcium sulfate with various dopants has also been investigated for OSL, [4][5][6][7][8] however the OSL properties of other sulfates are much less known. There have been only a few papers that have examined the OSL characteristics of sodium sulfate [9] or potassium sulfate (K 2 SO 4 ).…”