New Lead Free Perovskites with a Diffuse Phase Transition: NaNbO_3 Solid Solutions

摘要

Some of ( 1― x)NaNbO_3 ― (x) ABO_3 perovskite solid solutions exhibit a dramatic diffusion of the dielectric permittivity e' maximum and relaxor-type behavior when the second component concentration exceeds a threshold value x_0. The concentration phase transition to the relaxor-like phase is abrupt (of the first order kind) that is seen from the step in the dependence of the ε′(T) maximum temperature, T_m, on x. The precursor of this transition is a giant (up to KM) K) temperature hysteresis of ε′(T). Some relaxor-like properties appear even at x < X_0 in the course of cooling while disappear in the course of heating. The experimental data obtained are qualitatively described within a Landau-type phenomenological approach, assuming the relaxor-type behavior to be local stress-induced.