Phase Transition of High-Surface-Area Glycol-Thermal Synthesized Lanthanum Manganite

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 degrees C and a calcination temperature of up to 1000 degrees C, resulted in a single-phase perovskite, LaMnO3 validated using X-ray diffraction. Significant changes in unit cell volumes from 58 to 353 angstrom(3) 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(2)/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 LaMnO3 at different calcination temperatures are compared, and first-principles calculations suggest a geometric optimization of the cubic and rhombohedral perovskite structures.

Automated summary

Cubic and rhombohedral phases of lanthanum manganite were synthesized using a high-pressure reactor. The synthesized LaMnO3, validated through X-ray diffraction, exhibited significant structural transformation from the cubic to the rhombohedral phase, resulting in changes in unit cell volumes. Transmission electron microscopy analysis confirmed small particle sizes, no agglomeration, and good crystallinity. The material's particle characteristics, high purity, and high surface area make it suitable for important technological applications, including the synthesis of perovskite oxides.