Microstructural changes in a polycrystalline, semiconducting oxide under DC electric fields

Microstructural changes have been examined in a polycrystalline, semiconducting oxide, e.g., CoO, under de electric fields in an air-electrode condition. A change always starts at a singularity such as an interface or phase boundary where the divergence of partial cationic current does not vanish (i.e., del . i(ion) not equal 0). The changes (at del . i(ion) < 0, in particular) are characterized by the growth of the oxide beyond the permeable, original boundary of the system oxide, the grain growth and densification of the initially porous matrix, and the growth of a single-crystalline region at the expense of the polycrystalline matrix. These are qualitatively explained by chemical diffusion that is caused by the electrotransport-induced, chemical polarization at those singularities.