La_(1-x)Te_xMnO_3晶格结构的X射线粉末衍射分析

XRD analysis on lattice structure of La_(1-x)Te_xMnO_3

通过X射线粉末衍射数据,用Rietveld精修方法分析了Te部分替换LaMnO3中La后,其晶格参数及其结构对称性所发生的变化.结果表明:Te掺杂LaMnO3系列样品具有R3C的晶格结构对称性,其MnO6八面体晶格还产生了伸张畸变,畸变程度随Te掺杂量的增加而增大.此外根据Mn—O—Mn键角、eg电子能带的带宽、A位离子平均半径及A位离子尺寸失配度等的变化特点,推测Te掺杂LaMnO3样品除居里温度等相变物理量将随x增加而非线性变化外,还可能产生自旋玻璃态、相分离等宏观现象.

Based on X- ray powder diffraction data, the lattice structure and symmetry of La1-x Tex MnO3 （0.04 ≤ x ≤ 0.2） have been analyzed by Rietveld refining method, the results show that all samples structure have a rhombohedral symmetry with space group R 3^-C, and the lattice of MnO6 oetahedron has a stretching distortion due to the difference in cation size. Besides, the degree of structure distortion is closely related to Te content and can be depicted with the following three factors： the Mn--O--Mn bond angle θMn-O-Mn, the average A-site radius （ rA ） and the A-site size mismatch σ2 . According to the changing trend of these factors, several conjecture on physical properties are discussed, including the Curie temperature, spin-glass and phase separation etc.