KINETIC DEMIXING OF HETEROVALENTLY DOPED COO IN AN ELECTRICAL-FIELD

The steady state demixing of an initially homogeneous heterovalently d oped transition metal oxide (A,B)O in an electrical field is studied t heoretically and experimentally. Experimental results for the demixing of gallium-doped cobalt oxide, (Co1-xGax)O, where the dopant becomes enriched at the anode side are presented. By using a defect model for the doped oxide and the five-frequency model for impurity diffusion, i t can be shown that the enrichment of Ga at the anode is due to a nega tive apparent effective charge of the Ga3+ ions, which is caused by de fect-dopant interactions.