两步熔盐合成技术制备片状SrTiO_3晶体

Tabular SrTiO_3 Crystal Prepared by Two-step Molten Salt Method

采用两步熔盐法制备钙钛矿结构的片状SrTiO。晶体，利用XRD、SEM等手段研究了Sr3Ti2O2和SrTiO3晶粒的形成过程和微观形貌。结果表明，在SrCO3-TiO2-KCI体系中，片状Sr3Ti2O7的形成分两步进行，先由SrCO3、TiO2反应生成细小的Sr3Ti2O7相颗粒，再通过溶解一析出反应进行晶粒取向性生长，最终成为以（001）为主面的片状晶粒。1200℃保温4h后得到长10～20μm、厚约3μm的片状Sr3Ti2O7晶体。在Sr3Ti2O7-TiO2-KCl体系中，发现含Ti、Sr、O、K的晶须状中间化合物，同时出现较多等轴状SrTiO3颗粒，而且片形SrTiO3晶体较其前驱体Sr3Ti2O7有所增厚。这表明片形SrTiO3晶体的形成主要是Sr3Ti2O7因Sr、O析出产生切变而成，TiO2能够促进Sr3Ti2O7中Sr、O的析出，KCI熔盐同时起着传质介质和反应助剂的作用。

Tabular perovskite SrTiO3 crystal was prepared by two-step molten salt synthesis in KCI flux. The phase formation and morphology evolution of Sr3Ti2O7 and SrTiO3 particles were investigated by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The formation of Sr3Ti2O7 platelets includes two stages in the SrCO3-TiO2-KCI systefm： the phase formation of fine Sr3Ti2O7 product through the solution and reaction of constituents, followed by the orientated growth with （001） as the primary plane through dissolution-precipitation process. The tabular Sr3Ti2O7 particles with a length of 10-20μm and thickness of about 3μm were obtained at 1200℃ for 4h. In the Sr3Ti2OT-TiO2-KCI system, the whisker Sr-Ti-O-K intermediate and many equiaxial SrTiO3 particles were observed, and the tabular SrTiO3 particles became thicker than its precursor. Based on these facts, it is inferred that SrTiO3 platelets are formed primarily through the shear transformation of Sr3Ti2O7 induced by leaching out Sr and O. TiO2 can promote the liberation of Sr and O from Sr3Ti2OT. KCI flux serves as the diffusion media and the reaction assistant.