Grain boundary engineering by shape-control of SrTiO3 nanocrystals

摘要

Since 1976, grain boundary engineering (GBE) has been used to improve the properties of a material (e.g., strength and corrosion resistance in polycrystalline materials). The concept of GBE is to produce a high population of special grain boundaries (coincidence-site lattice grain boundaries, CSL GBs) with certain misorientations to replace general GBs with a random misorientation. Previous studies have demonstrated that special GBs exhibit superior properties of low defect, and this promotes the strength and corrosion and oxidation resistance of materials. Compared with metals, only few studies have reported on the application of GBE to ceramics. The main problem is that ceramics are too brittle to undergo a thermomechanical process (conventional GBE process of metals) to orientate grains for special GBs. To the best of our knowledge, only 3% (near the random distribution of 1.5%) of Sigma 3 GBs, one of the common CSL GBs, has been reported for polycrystalline strontium titanate (SrTiO3). We suggested that a high population of approximately 9% Sigma 3 GBs can be achieved in polycrystalline SrTiO3 by controlling the shapes and surface planes of nanocyrstals in SrTiO3 (initial powder). In addition, the formation mechanism of CSL GBs is discussed. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.