In situ XRD study on oxygen-excess LaMnO3

For LaMnO3+delta with oxygen-excess nonstoichiometry, in situ X-ray diffractometry was performed under high temperatures and precisely controlled oxygen partial pressures, P-O2. A rhombohedral phase was observed under most experimental conditions. With temperature rising, the lattice volume increased linearly in a low temperature region; the coefficient of linear thermal expansion (CTE) was 1.06 x 10(-5) K-1. In a high temperature region, the temperature dependence of the lattice volume upwardly deviated from the linearity, indicating that the unit cell expanded upon decrease in excess oxygen. The nonstoichiometry coefficient of the linear isothermal expansion was calculated at 5 x 10(-2) using literature data on delta(T, P-O2). The rhombohedral distortion escalated with temperature and P-O2 decreasing. The dependence of cell volume and distortion on nonstoichiometry is well interpreted as the effect of variation in the ionic radius and tolerance factor. (C) 2004 Elsevier B.V. All rights reserved.

对于具有氧过量非化学计量比的LaMnO₃₊δ，在高温以及精确控制的氧分压P - O₂条件下进行了原位X射线衍射测量。在大多数实验条件下观察到菱方相。随着温度升高，在低温区域晶格体积呈线性增加；线性热膨胀系数（CTE）为1.06×10⁻⁵ K⁻¹。在高温区域，晶格体积随温度的变化向上偏离线性，这表明随着过量氧的减少，单胞膨胀。利用关于δ(T, P - O₂)的文献数据计算出线性等温膨胀的非化学计量系数为5×10⁻²。随着温度升高和P - O₂降低，菱方畸变加剧。晶胞体积和畸变对非化学计量比的依赖关系可很好地解释为离子半径和容忍因子变化的影响。（C）2004爱思唯尔有限公司。保留所有权利。