The effect of electric fields on grain growth in MgAl2O4 spinel

The application of electrostatic fields during processing of oxide ceramic microstructures was previously reported to enhance densification and grain growth. In this study effects of the externally applied electrostatic field strength on grain growth in MgAl2O4 were investigated. Free sintering of green bodies showed accelerated grain growth by about 20% in the presence of an applied nominal field strength of 0.95 kV/cm. In contrast to previous studies, annealing of dense microstructures in the presence of a nominal electric field strength as high as 2.22 kV/cm revealed no additional grain growth. A machine learning algorithm for grain size analysis enabled grain size distributions including up to 30,000 grains. Due to the resulting counting statistics for microstructure analysis, it was discovered that the applied electrostatic fields caused grain growth predominantly during the early stages of sintering, i.e., at lower green body densities, hence suggesting an enhancement of surface diffusion.