Grain-growth behaviour of perovskite materials has been studied in detail over the last decades. Particularly the correlation with defect concentrations was observed by changing the atmosphere and by doping. More recently, the impact of electric fields on microstructure evolution was investigated (e.g. flash sintering and SPS). The active mechanisms for these processes are still under debate. However, basic research in this field is very challenging, since the experiments suffer from a poor controllability. For example, if an electric current flows through a sample, the true temperatures and local electric field strengths are hard to estimate.
The present study connects defect concentrations to field-assisted microstructure evolution. The discussion is based on well-defined model experiments (i.e. no joule heating, since insulating electrodes block electric currents). It is shown that for strontium titanate the effects of an electric field can be well understood by combining the knowledge of field-free microstructural evolution, defect chemistry and polarization. Similar research was carried out in Titania. Careful variation of field strength, temperature as well as sintering atmosphere (oxidizing or reductive) was used to obtain insights to electric field assisted grain growth. Further, the influence of electric fields on grain growth stagnation was evaluated.