Thermoluminescence and photostimulated luminescence of calcium halophosphate doped with Eu

Calcium halophosphate doped with Eu, Ca5(PO4)3(F, Cl):Eu, was investigated by thermoluminescence, photoluminescence, and diffuse reflection in order to characterize the optical storage properties of this material. The different photoluminescence emission spectra of Eu3+ and Eu2+ in Ca5(PO4)3(F, Cl) were observed and in addition, the decay times of the corresponding transitions were determined. By application of X-ray radiation an efficient conversion of the dopant charge state from Eu3+ to Eu2+ could be achieved. The luminescence of Eu2+ can be optically stimulated with photon energies of 1.9 eV which is lower than the required energy for the direct excitation of the Eu2+ transition.