The crystal structure of lanthanum manganate(III), LaMnO₃, at room temperature and at 1273 K under N₂

Orthorhombic stoichiometric LaMnO₃ is prepared by heating rhombohedral LaMaO_3+δ under N₂ at 1173 K and cooling to room temperature under N₂. The thermal transformations of orthorhombic lanthanum manganate(III) were investigated using high-temperature X-ray powder diffraction. Transformations orthorhombic-cubic-rhombohedral were observed. The dependence of the unit cell parameters on temperature was determined. The crystal structures of LaMnO₃ at room temperature (orthorhombic) and at high temperature (rhombohedral at 1273 K in N₂) were determined using neutron powder diffraction.