Chang Yunfei, Ning Huanpo, Wu Jie, Zhang Shantao, Lü Tianquan, Yang Bin, Cao Wenwu
Condensed Matter Science and Technology Institute & School of Science, Harbin Institute of Technology , Harbin 150080, China.
Inorg Chem. 2014 Oct 20;53(20):11060-7. doi: 10.1021/ic501604c. Epub 2014 Oct 6.
To develop a better understanding of the mechanism responsible for topochemical microcrystal conversion (TMC) from Aurivillius SrBi4Ti4O15 precursors to perovskite SrTiO3 microplatelets, compositional/structural evolutions, morphological development, and reaction interface evolution of the (001) oriented SrBi4Ti4O15 microplatelets were investigated during the conversion process. The results show that multiple topotactic nucleation events of SrTiO3 occurred directly on the surfaces of SrBi4Ti4O15 above 700 °C, while reacting zones of intermediate phase(s) with less Bi(3+) contents were observed to form in the interior of SrBi4Ti4O15. Extensive exfoliation of the precursors occurred generally parallel to the (001) surfaces above 775 °C. At 950 °C, the original single-crystal SrBi4Ti4O15 platelet was replaced by a polycrystalline aggregate consisting of (001) aligned SrTiO3 crystallites and poorly crystallized intermediate phase(s). With further increasing the temperature or holding time, the SrTiO3 phase formed from related intermediate phase(s), and the aligned crystallites were sintered to form dense SrTiO3 with strong (001) orientation. The obtained SrTiO3 microplatelets preserved the shape of SrBi4Ti4O15 and show high chemical and phase purity. This TMC mechanism has general applicability to a variety of compounds and will be very useful for the design and synthesis of novel anisotropic perovskite crystals with high quality in the future.
为了更好地理解从奥里维利乌斯相SrBi4Ti4O15前驱体到钙钛矿相SrTiO3微片的拓扑化学微晶转变（TMC）的机制，研究了（001）取向的SrBi4Ti4O15微片在转变过程中的成分/结构演变、形态发展和反应界面演变。结果表明，在700℃以上，SrTiO3在SrBi4Ti4O15表面直接发生多次拓扑成核事件，同时观察到在SrBi4Ti4O15内部形成了Bi(3+)含量较低的中间相反应区。在775℃以上，前驱体普遍沿（001）面发生大量剥落。在950℃时，原来的单晶SrBi4Ti4O15片被由（001）取向的SrTiO3微晶和结晶不良的中间相组成的多晶聚集体所取代。随着温度的进一步升高或保温时间的延长，由相关中间相形成SrTiO3相，取向的微晶烧结形成具有强（001）取向的致密SrTiO3。所得的SrTiO3微片保留了SrBi4Ti4O15的形状，并具有高化学纯度和相纯度。这种TMC机制对多种化合物具有普遍适用性，对未来高质量新型各向异性钙钛矿晶体的设计和合成将非常有用。
