Topochemical reaction of SrTiO₃ platelet crystals based on Sr₃Ti₂O₇ platelet precursor in molten salt synthesis process

Molten salt synthesis (MSS) is an effective method to prepare anisotropic shaped single crystals. In this study strontium titanate (SrTiO₃) (ST) platelet crystals were successfully synthesized based on Sr₃Ti₂O₇ (S3T2) platelet precursor in MSS process. The objective is to identify the formation mechanism of SrTiO₃ platelet crystals based on Sr₃Ti₂O₇ platelet precursor. During the synthesis process of Sr₃Ti₂O₇ and SrTiO₃ crystals, the final sizes are strongly influenced by the sorts of alkali chloride medium. Sr₃Ti₂O₇ and SrTiO₃ crystals with 30-50 μm in edge length and ∼2 μm in thickness are obtained in KCl medium. The conversion of SrTiO₃ platelet crystals from Sr₃Ti₂O₇ platelet precursor is a topochemical process, including diffusion of Sr and O atoms, and reconstruction of SrTiO₃ blocks. In the topochemical process, TiO₂ is the driving force of diffusion of Sr and O atoms from Sr{single bond}O layer in Sr₃Ti₂O₇, which reacts with dissociative Sr²⁺ and O^2- to form SrTiO₃ in different positions: deposited at interior pores and surface of Sr₃Ti₂O₇, and dispersed in molten salt medium.