Structural Properties of Mechanically Activated Rare-Earth Manganites

The effect of mechanical processing in different types of activators on the structure and physicochemical properties of the oxides LnMnO3+δ (Ln = Sm, Nd, La) has been studied. The optimal modes of mechanical activation for transformation the oxides under consideration to nanostructured state have been defined. Mechanical processing has been shown to cause a significant change of Jahn-Teller distortion parameters and temperatures of the cooperative Jahn-Teller phase transition. The presence of connection between redox processes and destruction of orbital ordering has been demonstrated. Very low values (10 -21 -10 -24 m 2 /s) of the oxygen bulk diffusion coefficient have been obtained for the oxides under consideration in the temperature range of 400 - 750°C. The diffusion activation energies are close to 1 eV, indicating the oxygen diffusion proceeds through structural defects at these temperatures.