Paramagnetic centres in tungstate powders

The EPR-powder spectrum ofV _k -centres in CaWO₄ is simulated using the experimentally obtained principal values of theg-tensor. The influence of the finite linewidth ΔH on the resulting EPR-pattern is taken into account. With these results the existence ofV _k -centres in x-rayed microcrystalline tungstate powder is proved. The resonance of the² S _1/2-state of Pb³⁺-ions substitutionally incorporated on Ca²⁺-sites in CaWO₄ is measured in the powder spectrum. The optically and thermally stimulated valence state changes of the centres are studied and are shown to be correlated with the thermoluminescence glow curve.