Diffusion of Barium in Barium Oxide

Abstract

The self-diffusion of barium in single crystals of barium oxide has been measured as a function of temperature in the range from 550°K to 1520°K. Two diffusion processes were found. Measurement of the ionic mobility (with a tracer technique) showed that one of these processes was charge-transporting (∼2 electronic charges) and the other was not. At temperatures below 1350°K the diffusion was "structure sensitive" and could be affected by previous heat treatment. The temperature dependence for the non-charge-transporting diffusion was 11±2.2 ev above 1350°K and 0.44±0.03 ev below 1350°K. The corresponding figures for the charge-transporting diffusion were 12±2.3 ev and 0.3±0.05 ev. The surface diffusion constant for barium on barium oxide was also measured and had a temperature dependence of 0.16±0.03 ev.