Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

Abstract

This study investigates grain growth in the perovskite oxide strontium titanate in an electric field. The seeded polycrystal technique was chosen as it provides a sensitive and controlled setup to evaluate the impact of different parameters on grain growth due to the well‐defined driving force for grain growth. Current blocking electrodes were used to prevent Joule heating. The results show faster grain growth, and thus, higher grain‐boundary mobility at the negative electrode. It is argued that the electric field causes point‐defect redistribution, resulting in a higher oxygen vacancy concentration at the negative electrode. The local oxygen vacancy concentration is suggested to affect the space‐charge potential at the grain boundaries. A thermodynamic treatment of the grain‐boundary potential at a grain boundary without field shows that for a high oxygen vacancy concentration less space‐charge and less accumulation of cationic defects to the boundary occurs. Therefore, at the negative electrode, a higher oxygen vacancy concentration results in less space‐charge and less accumulation of cationic defects. The lower degree of defect accumulation requires less diffusion of segregated defects during grain‐boundary migration, so that at the negative electrode faster grain growth is expected, as found in the experiments.

Enhancement of the SrTiO3 Surface Reactivity by Exposure to Electric Fields

“…If microwave‐assisted syntheses covered a pivotal role in the last decades, the use of electric and magnetic fields recently emerged as novel strategy towards synthesis and the processing of inorganic materials . In addition to the energy‐saving character, these methods are very appealing because of i) the possibility to synthesize materials that cannot be prepared by conventional methods, ii) the design of materials with specific microstructure and textures and iii) control of defect formation and mobility …”

“…In a more recent publication Rheinheimer et al. showed that the application of an electric field on SrTiO 3 caused point defect redistribution, affecting the space charge potential at the grain boundaries …”

Electric-field-assisted processing of ceramics: Nonthermal effects and related mechanisms

“…In SrTiO 3 , recent model experiments used blocking electrodes to prevent current-induced Joule heating and to isolate nonthermal effects. 45,46 The growth of single-crystalline seeds into polycrystals was observed with well-controllable driving forces for grain growth. 47 An electric field ( ≤ 5 × 10 4…”

Comparing hydrothermal sintering and cold sintering process: Mechanisms, microstructure, kinetics and chemistry

“…The higher oxygen vacancy concentration typically promotes the grain growth because it provides higher diffusivity [33]. The oxygen vacancy level is also critical for the grain boundary mobility that affects the grain growth [66].…”