New dielectric and ferroelectric solid solution of (1-x)Ba(Mg _1/3Nb_2/3)O₃-xPbTiO₃ with morphotropic phase boundary

A new solid solution of (1-x)Ba(Mg_1/3Nb_2/3)O ₃-xPbTiO₃ [(l-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 x = 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 the diffuse maximum of high permittivity shifting to higher temperature with increasing frequency. 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.