Reversibility of structure phase transitions in LaMnO3+δ manganite under heat treatment

The effect of heat treatment on the formation and mutual transitions of the structure modifications in the 57Fe-doped LaMnO3+δ manganite has been experimentally investigated by X-ray diffraction analysis and Mössbauer spectroscopy. It has been found out that the successive heat treatments in vacuum and in air provide controlled reversible structural transformations between rhombohedral and two orthorhombic modifications. Variations in the oxygen environment configuration of cations and in crystal-chemical packing have been analyzed at reversible phase transitions. The experimental evidences confirming the presence of extra oxygen in the structure modifications of lanthanum manganite have been obtained.