THEORY OF FERROELECTRICITY IN THE TETRAGONAL PHASE OF PURE AND IRON-DOPED BATIO3 DUE TO THE LATTICE DEFORMATION

The ferroelectricity in the tetragonal phase of pure and iron doped Ba TiO3, namely BaTiO3:Fe, is discussed quantitatively from the dipole-di pole interaction caused by the strong local field acting on the consti tuent ions. In this microscopic model, only the Ti ions localised at t he center of the lattice are assumed to have the spontaneous shift. Th e ferroelectric-paraelectric phase transition in BaTiO3 is also analyz ed. It is found that the ferroelectricity and the order of the phase t ransition in BaTiO3 are in good agreement with the experimental data.