The activation energy for clustering of Pb2+vacancy pairs in NaCl and a comparison with the diffusion activation energy

Abstract

An accurate measurement has been made of the activation energy (0.85 eV) of the aggregation of Pb²⁺ vacancy pairs in NaCl:Pb²⁺, using measurements of the intensity of the dielectric absorption. This is compared with the enthalpy of diffusion (0.98 eV) for a Pb²⁺ vacancy pair in NaCl. The significance of the difference is discussed in relation to the concentration of dimers which may occur in doped alkali halides.