Common features of gallium perovskites

The Czochralski and floating zone methods have been used to grow single cry stals of gallium perovskites solid solutions with rare earth elements La, P r, Nd, Sm and with Sr. The structure of the crystals has been investigated by powder X-ray, synchrotron radiation and neutron diffraction methods over a wide temperature range. The unit cell volume at room temperature varies from approximately 228 to 236 Angstrom (3) in Sm0.75Nd0.25GaO3 and La0.88Sr 0.12GaO3-delta, respectively. Position of atoms in the unit cell and evolut ion of perovskite lattice deformation induced by continuously varying avera ge rare earth ionic radius is discussed. The unit cell parameters including atoms positions, thermal expansion coefficients, segregation coefficients and phase transition temperature scale with the unit cell volume in all inv estigated crystals. All these parameters may be represented as a function o f average ionic radius of rare elements, however, this value is not well de termined in these compounds because of ill determined coordination number.