Anyanwu Victor O, Friedrich Holger B, Mahomed Abdul S, Singh Sooboo, Moyo Thomas
School of Chemistry and Physics, Westville Campus, University of KwaZulu-Natal, Durban 4000, South Africa.
Materials (Basel). 2023 Feb 2;16(3):1274. doi: 10.3390/ma16031274.
Cubic and rhombohedral phases of lanthanum manganite were synthesized in a high-pressure reactor. A mixture of La and Mn nitrates with ethylene glycol at a synthesis temperature of 200 °C and a calcination temperature of up to 1000 °C, resulted in a single-phase perovskite, LaMnO validated using X-ray diffraction. Significant changes in unit cell volumes from 58 to 353 Å were observed associated with structural transformation from the cubic to the rhombohedral phase. This was confirmed using structure calculations and resistivity measurements. Transmission electron microscopy analyses showed small particle sizes of approximately 19, 39, 45, and 90 nm (depending on calcination temperature), no agglomeration, and good crystallinity. The particle characteristics, high purity, and high surface area (up to 33.1 m/g) of the material owed to the inherent PAAR reactor pressure, are suitable for important technological applications, that include the synthesis of perovskite oxides. Characteristics of the synthesized LaMnO at different calcination temperatures are compared, and first-principles calculations suggest a geometric optimization of the cubic and rhombohedral perovskite structures.
在高压反应器中合成了锰酸镧的立方相和菱方相。将镧和锰的硝酸盐与乙二醇混合，在200℃的合成温度和高达1000℃的煅烧温度下，得到了单相钙钛矿LaMnO，并用X射线衍射进行了验证。观察到晶胞体积从58 Å显著变化到353 Å，这与从立方相到菱方相的结构转变有关。这通过结构计算和电阻率测量得到了证实。透射电子显微镜分析表明，颗粒尺寸小，约为19、39、45和90 nm（取决于煅烧温度），无团聚现象，结晶度良好。由于PAAR反应器的固有压力，该材料的颗粒特性、高纯度和高比表面积（高达33.1 m²/g）适用于包括钙钛矿氧化物合成在内的重要技术应用。比较了不同煅烧温度下合成的LaMnO的特性，第一性原理计算表明立方和菱方钙钛矿结构存在几何优化。
