Diffusion of Barium in Barium Oxide

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.