Association of defects in lead chloride and lead bromide: Ionic conductivity and dielectric loss measurements

Abstract

The ionic conductivity data of pure and doped lead bromide without associated defects are used in order to explain the anomalous conductivity behaviour of copper (I) bromide and lead oxide-doped lead-bromide crystals. In these crystals precipitated dopant and associated defects are present. The association enthalpy, and enthalpies| of solution for free defects and for associated defects in lead bromide are calculated from the concentration and temperature dependence of the ionic conductivity, respectively. A detailed comparison has been made between the ionic conductivity data and dielectric loss measurements on both lead chloride and lead bromide. Associated defects of the type (MePb·VX)× and (Ox·Vx)×, (X = Cl, Br) as found from the conductivity data, are confirmed by the dielectric loss measurements. For the copper (I) bromide-doped lead-bromide crystals a relaxation process is proposed because of hopping electrons.