Dipole effects in AWO4(A=Pb,Cd) luminescent crystals

Temperature dependences of permittivity (ε) at a frequency of 1 kHz and thermostimulated depolarization (TSD) current were studied for undoped AWO4(A=Pb,Cd) single crystals in a temperature range of T=290-550K. Two series of TSD maxima were observed in the 290-350 and 380-550 K ranges. In the case of previously polarized PbWO4 crystals, the ε(T) curve maximum was observed at about 320 K. The results obtained indicate that in the AWO4 crystals the active ion-electron processes are realized. These processes are in particular caused by dipole associates and isolated electrical active defects and by charge carriers exchange between them. The characteristics of PbWO4 and CdWO4 are compared.