Crystal growth and electrical conduction of PbMoO4 and PbWO4

Abstract

The phenomenon of the coloration of Czochralski grown single crystals of PbMoO4 and PbWO4 is discussed. This coloration is supposed to be related to an intrinsic point defect. We propose that during the crystal growth a loss of oxygen occurs, and consequently, oxygen deficient crystals are produced. The existence of electronic charge carriers at high temperatures and ionic majority defects in the oxygen sublattice is confirmed by conductivity measurements. The color center is supposed to be an oxygen vacancy that has trapped one or two electrons. On the basis of this simple model, various aspects of the coloration can be understood.