Impact of AC and DC Electric Fields on the Microstructure Evolution in Strontium Titanate

Herein, the impact of AC and DC electric fields on microstructure evolution in strontium titanate is investigated. The focus is on nonthermal effects by using current-blocking electrodes. The seeded polycrystal technique allows investigating the impact of a DC electric field on grain growth for different grain-boundary orientations and the impact of the surrounding atmosphere. As in previous studies, faster grain growth is observed at the negative electrode. This effect is stronger for the (100) orientation and in reducing atmosphere. In AC electric field at 1450 °C, a low-enough frequency results in faster grain growth at both electrodes. These findings agree well with previous studies, where an electromigration of oxygen vacancies is found to cause a local reduction at the negative electrode, resulting in less space charge, less cationic segregation, and a higher grain-boundary mobility. At 1500 °C, AC electric fields are found to cause a complete grain growth stagnation at very small grain sizes. This behavior is unexpected; the physical reasons are not clear. Herein, a brief study of sintering in DC electric field reveals slightly faster sintering if a field is applied.