Papers by Author: M.A. Ivanov

Abstract: An investigation has been undertaken of the structural characteristics of the manganese oxides to understand these characteristics affected by mechanochemical treatment conditions. Chemically pure manganese (II, III) oxides and their mixtures were used as the initial components.

Abstract: Specific features of the structural phase transitions of the first order were investigated in nanosized crystals with Jahn-Teller ions. As an example the phase transitions of martensite type with changes in symmetry from a cubic to a tetragonal one have been considered. The Kanamori model was used to take into account the size of nanocrystallites and the distribution of cations over non-equivalent crystallographic sublattices in such systems. It was shown the temperature and the latent heat of the transition decrease significantly for the nanoscaled grains. A possibility of multi-phase state for nanocrystalline materials was considered.

Abstract: Phase diagrams of mixed crystal systems exhibiting the cooperative Jahn–Teller effect are investigated. The competition of Jahn–Teller interaction with a) the preference energy of cation distribution over nonequivalent sublattices or b) stabilization energy of 3d-ion valence configuration is considered. The developed model enables to explain the nature of equilibrium and metastable states, the variety of phase diagrams and its special features in crystals with the competing interactions.