Synthesis and thermoluminescence of Ce-doped CaF2 phosphor: Study of defect centers responsible for the TL emission by EPR analysis

Abstract

We present here the thermoluminescence (TL) properties of Ce-doped CaF2 (CaF2:Ce) phosphor synthesized by combustion of the precipitate formed from the addition of NH4F to (Ca(NO3)2)⋅4H2O. The structure analysis of the synthesized sample was carried out by X-ray diffraction (XRD) technique. The CaF2:Ce phosphor shows an intense peak at about 120 °C and a low-intensity peak at 280 °C. Both peaks' thermoluminescence (TL) intensity was observed to increase with γ-dose. The kinetic parameters of TL peaks were calculated for CaF2:Ce phosphor using the Tm-Tstop and deconvolution methods. Electron paramagnetic resonance (EPR) is utilized to identify the defect centers formed in γ-irradiated CaF2:Ce phosphor and also to infer the defect centers involved in the TL process. The presence of two defect centers is inferred and center I has a g-value equal to 2.018 and is identified as an O− ion. The O− ion correlates with the TL peak at 120 °C. Center II with a g-value of 2.0057 is ascribed to a radiation-induced Fe3+ ion and is observed to relate to the high-temperature TL peak at 280 °C. The UV–Vis optical absorption of pure CaF2 and Ce-doped phosphors was investigated.