A New Solid Solution of (1-x)Ba(Mg1/3Nb2/3)O3-xPbTiO3 with Dielectric, Relaxor and Ferroelectric Properties

A new solid solution of (1-x)Ba(Mg_1/3Nb_2/3)O₃-xPbTiO₃ [(1-x)BMN-xPT] has been synthesized in the form of ceramics by solid state reactions and characterized by means of X-ray diffraction, dielectric spectroscopy and ferroelectric measurements. A partial solid state phase diagram of the binary system is established. It exhibits a morphotropic phase boundary region in the composition range between x = 0.71 and 0.74. The dielectric permittivity of BMN has been greatly enhanced by the substitution of PT. The ceramics of 0.4BMN-0.6PT show typical relaxor ferroelectric behavior with a strong dispersion of the maximum of dielectric permittivity (ε´) appearing around the temperature of T_m, which shifts towards higher temperatures with increasing frequency. The variation of T_m with frequency follows the Vogel-Fulcher relationship. A deviation from the Curie-Weiss law is observed above T_m. Instead, the variation of 1/ε´ with temperature above T_m satisfies a Lorentz-type function. With further increase of the PT-content, the permittivity peaks become sharper and frequency-independent, indicating a ferroelectric phase transition, the temperature of which (Tc) increases with x. Thus, the transformation from a simple dielectric, to relaxor and to ferroelectric phase has been demonstrated in this solid solution system.