Modification of grain boundary structure of SrTiO3 using hydroxyl additives

Strontium titanate (SrTiO₃) is a typical perovskite material due to its crucial properties such as a good dielectric constant and favorable conductivity. Early studies reported that hydroxyl (OH) groups can manipulate the shape of the SrTiO₃ surface and control the crystal growth by changing the surface energy. This concept may be used to increase the population of (111) surfaces to form more Σ3 grain boundaries, which have lower energy for high ionic conductivity. In this study, two common OH additives, glycerol and 1,2-propanediol, were used for preparation of SrTiO₃ powders. SrTiO₃ powders were synthesized by spray pyrolysis and then sintered to form polycrystalline SrTiO₃. The results showed that the additive-treated SrTiO₃ powders had a higher population of (111) planes and exhibited higher conductivity than did un-treated powder. In addition, the highest population of Σ3 grain boundaries was generated by 1,2-propanediol treatment (11.0 ± 0.8%) of SrTiO₃, followed by glycerol treatment (10.0 ± 0.3%) and no treatment (2.5 ± 0.2%), respectively.