Structure and dielectric properties of Na1/2Bi1/2TiO3-BaTiO3 solid solutions

Dielectric properties, polarization and x-ray diffraction are studied for (1-x)Na_1/2Bi_1/2TiO₃-xBaTiO₃ solid solutions in a concentration range above the morphotropic phase boundary. It is showed that all the studied compositions have tetragonal structure with maximal tetragonality slightly above the morphotropic phase boundary. Ferroelectric relaxor behavior is observed in a wide concentration range of BaTiO₃. Stability of the relaxor state decreases with increasing BaTiO₃ concentration, but only for compositions with low Na_1/2Bi_1/2TiO₃ content the normal ferroelectric-paraelectric phase transition, which is characteristic to pure BaTiO₃, occurs. Mechanisms, which influence the change of the phase transition character and promote the appearance of the relaxor state, are discussed. The phase diagram of (1-x)Na_1/2Bi_1/2TiO₃-xBaTiO₃ is revised.