Theoretical aspect on relaxor appearance in mixed perovskite-oxides

In mixed perovskite-oxides with displacive type phase transition, the phenomenological theory is tried to make clear the conditions for relaxor appearance, and is extended to combine with a microscopic approach in order-disorder type transition. Relaxor region near the morphotropic phase boundary (MPB) is lead depending on the anisotropy of polarization, and under conditions similar to those for relaxor perovskite-type oxides, the microscopic approach is attempted in success for order-disorder type mixed crystals. Relaxor behaviors are found at a boundary region through the gradual growth of wave number to make the energy minimum in X-ray diffuse scattering and an extremely broad NMR-NQR spectrum, which are in quite different forms from those of both glass phase and other boundary regions. In perovskite-oxides, the definition of relaxor properties is discussed at the MPB region by combining the phenomenological theory with this microscopic analysis.