It was recalled that the linear transport theory assumed that, in a semiconducting oxide, an ionic flow could be caused not only by the ionic electrochemical potential gradient but also, indirectly, by the electronic electrochemical potential gradient. On the other hand, it was generally believed that the latter effect was negligible. However, it had recently been shown experimentally that the above interfering effect was not negligible in the present oxide.

H.I.Yoo, J.H.Lee: Solid State Ionics, 1995, 80[1-2], 5-9