Department of Materials Engineering, Indian Institute of Science, Bangalore 560012, India.
J Phys Condens Matter. 2010 Feb 24;22(7):075901. doi: 10.1088/0953-8984/22/7/075901. Epub 2010 Jan 29.
The structures of (1 - x)Na(0.5)Bi(0.5)TiO(3)-(x)CaTiO(3) at room temperature have been investigated using neutron powder diffraction and dielectric studies. The system exhibits an orthorhombic (Pbnm) structure for x ≥ 0.15 and rhombohedral (R3c) for x ≤ 0.05. For x = 0.10, though the neutron diffraction pattern shows features of the orthorhombic (Pbnm) structure, Rietveld refinement using this structure shows a drastic reduction in the in-phase tilt angle (∼4°) as compared to the corresponding value (∼8°) for a neighbouring composition x = 0.15. The neutron diffraction pattern of x = 0.10 could be fitted equally well using a two-phase model (R3c + Pbnm) with orthorhombic as the minor phase (22%), without the need for a drastic decrease in the in-phase tilt angle. The dielectric studies of x = 0.10 revealed the presence of the polar R3c phase, thereby favouring the phase coexistence model, instead of a single-phase Pbnm structure, for this composition.
室温下（1-x）Na(0.5)Bi(0.5)TiO(3)-(x)CaTiO(3) 的结构已通过中子粉末衍射和介电研究进行了研究。该系统对于 x ≥ 0.15 表现为正交（Pbnm）结构，对于 x ≤ 0.05 表现为三方（R3c）结构。对于 x = 0.10，尽管中子衍射图谱显示出正交（Pbnm）结构的特征，但使用该结构进行 Rietveld 精修表明，同相倾斜角（∼4°）急剧减小，与相邻组成 x = 0.15 的相应值（∼8°）相比。x = 0.10 的中子衍射图谱可以使用两相模型（R3c + Pbnm）同样好地拟合，其中正交相为次要相（22%），而无需急剧减小同相倾斜角。x = 0.10 的介电研究揭示了极性 R3c 相的存在，从而有利于相共存模型，而不是单一的 Pbnm 结构，对于该组成。
