Effect of electric fields on solid-state reactions between oxides

Abstract

The solid-state reaction between CaO and AI₂O₃ in intimately mixed powders and pressed polycrystalline pellets to form a series of calcium aluminates is assisted by the application of external d.c. electric fields. The formation of all the aluminate phases is particularly enhanced in the vicinity of the positive electrode. The major effect of the electric field is probably to assist the diffusion of Ca into AI₂O₃, and the results can be qualitatively explained in terms of a simple diffusional model which takes account of the orientation of the reactant grains relative to each other and to the electric field vector. Possible effects of field-induced sintering and the anion packing density of the various product phases are also discussed.