Mishra Sanjay Kumar, Ranjan Rajeev, Pandey Dhananjai, Stokes H T
School of Materials Science and Technology, Institute of Technology, Banaras Hindu University, Varanasi-221005, India.
J Phys Condens Matter. 2006 Feb 15;18(6):1885-98. doi: 10.1088/0953-8984/18/6/006. Epub 2006 Jan 24.
Results of a powder x-ray diffraction study are presented to show that the so-called 'nearly cubic' phase region of Sr(1-x)Ca(x)TiO(3), in fact, corresponds to two different types of crystal structures. The 'nearly cubic' phase occurring in the composition range 0.35<x<0.41 is antiferroelectric in nature and its most plausible space group is Pbcm, while the crystal structure of the 'nearly cubic' phase for 0.41≤x<0.70 belongs to the space group Pbnm. This space group persists up to x = 1.0, even though the 'nearly cubic'-like features disappear for x≥0.70. There are two other phase boundaries which occur around 0.05<x<0.06 and 0.35<x<0.36 and correspond to the change of structures with space groups Pm3m to Ibmm and Ibmm to Pbcm, respectively.
粉末X射线衍射研究结果表明，Sr(1-x)Ca(x)TiO(3)所谓的“近立方”相区实际上对应两种不同类型的晶体结构。在0.35<x<0.41组成范围内出现的“近立方”相本质上是反铁电的，其最合理的空间群是Pbcm，而0.41≤x<0.70时“近立方”相的晶体结构属于空间群Pbnm。即使对于x≥0.70，“近立方”状特征消失，这个空间群一直持续到x = 1.0。还有另外两个相界，分别出现在0.05<x<0.06和0.35<x<0.36附近，分别对应空间群从Pm3m到Ibmm以及从Ibmm到Pbcm的结构变化。
