It was noted that a non-uniform charged defect distribution could arise in single-phase, originally uniform, mixed ionic-electronic conductors which were subjected to gradients of chemical potential and/or to an applied voltage. The electronic defects could form graded n, graded p regions, and pn or pin junctions, but this did not always require the existence of a space charge. In the case of a zero space charge, the I-V characteristics of the pn junctions were very different to those of normal pn diodes. The electronic defect distribution for the main types of mixed ionic-electronic conductors were considered, and the effects of a chemical potential gradient and of an applied voltage under steady-state conditions were demonstrated.

I.Riess: Solid State Ionics, 1995, 75, 59-66