Morphotropic Phase Diagram and Dielectric and Ferroelectric Properties of (1−<i>x</i>)Ba(Sc_1/2Nb_1/2)O_₃−<i>x</i>PbTiO₃ Solid Solution

Abstract

The solid solution of (1−x)Ba(Sc1/2Nb1/2)O3−xPbTiO3 (0 ≤ x ≤ 1) has been synthesized in the perovskite structure by solid-state reaction in the form of ceramics and characterized by means of X-ray diffraction, dielectric spectroscopy, and ferroelectric measurements. A partial solid-state phase diagram (T ≈ x) of the binary system is established based on the X-ray and dielectric measurement. A morphotropic phase boundary (MPB) region is found within the composition range of x = 0.61−0.65. The dielectric permittivity is enhanced greatly by increasing the PT content, reaching peak values for the MPB compositions. The ceramics of 0.42BSN-0.58PT show typical relaxor ferroelectric behavior with diffuse maxima of permittivity, which shift to higher temperatures when increasing the frequency. With further increase in PT amount, the dielectric permittivity peaks become sharper and frequency independent, indicating a ferroelectric phase transition, the Curie temperature (Tc) of which increases accordingly. The change in dielectric properties reveal the transformation from dielectric to relaxor and to ferroelectric behavior, induced by composition in the solid-solution system.