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(Mg1/3Nb2/3)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 Tm, which shifts towards higher temperatures with increasing frequency. The variation of Tm with frequency follows the Vogel-Fulcher relationship. A deviation from the Curie-Weiss law is observed above Tm. Instead, the variation of 1/ε' with temperature above Tm 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.