Chemical Diffusion in Mixed Conductors under Various Boundary Conditions. I.

Abstract

One-dimensional diffusion equation for chemical or ambipolar diffusion in ionic-electronic mixed conductors is solved under various experimental conditions. (1) Electronic or ionic electrodes are set at arbitrary positions of specimen having various end conditions: (A) Both ends of specimen are left free. (B) Large blocks of the material which is the same as that of the specimen are attached at both ends so that the concentration of ions at the ends is kept constant. (C) Small blocks of the specimen material are attached at both ends. (2) Atomic electrodes—combined electronic and ionic electrodes—are used. (3) Constant voltage is applied between two ionic electrodes attached at both ends of the specimen, instead of current intensity being kept constant. Experiments are carried out on silver chalcogenides, typical mixed conductors, showing good agreement with calculation results.