钙钛矿-锶钛矿-钠镧钛矿体系化合物晶体化学的研究概况

A Review in Crystal Chemistry of Compounds in the Perovskite-Tausonite-Loparite System

钙钛矿 锶钛矿 钠镧钛矿三元系是钙钛矿族矿物的典型代表。常温常压下CaTiO3为Pbnm结构,但随温度增高可分别相变为I4/mcm和Pm3m结构;SrTiO3的稳定结构是Pm3mI4/mcm相;Na1/2Ln1/2TiO3的结构则随Ln代表的元素种类不同而有所差异。三个端员组分在压力下的结构变化均没有明确的结论。在三个二元系中,只有CaTiO3 SrTiO3体系研究较深入,并已给出了T X相图。本文从样品的合成实验及高温和高压原位测量等方面展望钙钛矿型化合物的晶体化学研究及其意义。

At ambient condition, CaTiO_3 adopts the Pbnm structure and will transfer to I4/mcm and Pm3m with increasing temperature,while SrTiO_3 is with Pm3m structure and transfers to I4/mcm at low temperature. The structure of loparite with general formula Na_(1/2)Ln_(1/2)TiO_3 depends mainly on the elements at the Ln site. However, the agreement on the structures of the end members under pressures has not been achieved yet at this moment. In this triple system, only the CaTiO_3-SrTiO_3 compounds have been extensively studied.Future research on the crystal chemistry of perovskite compounds is expected along the route of sample synthesis and in-situ measurement.The significance of this triple perovskite system is also briefly discussed in the view of research method and geological importance.