DIFFUSION OF NI IN THE BULK AND ALONG DISLOCATIONS IN NIO SINGLE-CRYSTALS

Diffusion profiles of 63Ni tracer in single crystals of NiO following anneals at 522°-1000°C have been determined by a radio-frequency sputter-sectioning technique. The profiles were analysed in terms of diffusion in the NiO lattice, D1, together with a contribution from dislocations in low-angle grain boundary arrays. The lattice diffusion coefficient and the diffusion coefficient for Ni diffusion in a dislocation, Dd, at an oxygen pressure of 1 atm are given by: D1=0.022 exp {−59 000/RT} cm2 s−1 (522°–1400°C), and Dd=0.26 exp {−46 000/RT}cm2 s−1 (522°-800°C), where the activation energies are in cal mole−1. Diffusion in the dislocation takes place by a vacancy mechanism within a vacancy-rich pipe of radius ∼10−7 cm surrounding the dislocation. © 1979 Taylor & Francis Group, LLC.