Electric field driven solid state reactions—reaction kinetics and the influence of grain boundaries on the interface morphology in the system MgO/MgIn2O4/In2O3

Abstract

Under working conditions ceramic materials are often exposed to high electrical fields in addition to high temperatures. For this reason we investigate the reaction kinetics and the morphological evolution of the moving interfaces of a spinel forming solid state reaction under the influence of an external electric field. A model, based on linear transport theory and defect thermodynamics is used to analyse the results. Compared to a reference reaction without external electric field, the reaction rate is strongly enhanced and the morphology of the product layer has significantly changed. Systematic kinetic studies confirm a linear law with a constant growth rate for the electric field-driven spinel formation. The role of grain boundaries as fast diffusion paths is highly emphasised. A relationship between large angle grain boundaries in the product phase and the local reaction kinetics is pointed out. An analysis of the reaction rate indicates an unusually high transference for the trivalent ions compared to the divalent ions in the grain boundaries of the spinel phase.