On the luminescence properties of CaSO4:Ce

The luminescent properties of cerium doped calcium sulphate are studied: fluorescence and excitation spectra, optical absorption and thermoluminescence (TSL). It is know that, in rare earth doped CaSO4, only cerium induces a strong 400 deg. C TSL peak readout, as mentioned by Nair et al. In CaSO4:0.2% Ce samples synthesised under oxidising conditions, the recovery step of Ce3+ fluorescence is correlated with the 400 deg. C TSL peak readout. Our results indicate that an oxidation of Ce3+ ion does occur under X-irradiation (Ce3+ R Ce4+), followed by a complete return to the trivalent state after thermal annealing at about 500 deg. C; our results confirm the hypothesis of Nair et al that Ce3+ ions are oxidised by ionising irradiation. So, a pure redox reaction seems the most probable for the 400 deg. C TSL peak of CaSO4:Ce. Moreover, the use of the 400 deg. C TSL peak for high temperature dosimetry applications is discussed. (author)