Grain growth in weak electric fields in strontium titanate: Grain growth acceleration by defect redistribution

The impact of DC electric fields on grain growth in strontium titanate is investigated between 1350 degrees C and 1550 degrees C for fields of up to 50 V/mm. To prevent joule heating by electrical currents, insulating Al2O3 plates separate electrodes from samples. The seeded polycrystal technique is used, which allows evaluating gradients induced by electric fields. The growth direction of the single crystalline seeds is perpendicular to the electric field; hence electrostatic forces do not influence its growth. Below 1425 degrees C, the influence of electric fields is very weak. Above 1425 degrees C the field results in an increase of the grain boundary mobility at the negative electrode. The enhancement of the boundary mobility at the negative electrode is attributed to electric field induced defect redistribution. Oxygen vacancies migrate towards the negative electrode, while strontium vacancies accumulate at the positive electrode. This defect redistribution is connected to the defect chemistry dependent grain growth in strontium titanate. (C) 2016 Elsevier Ltd. All rights reserved.