Annealing-Dependent Morphotropic Phase Boundary in the BiMg 0.5 Ti 0.5 O 3 -BiZn 0.5 Ti 0.5 O 3 Perovskite System.

The annealing behavior of (1- x )BiMg 0.5 Ti 0.5 O 3 - x BiZn 0.5 Ti 0.5 O 3 [(1- x )BMT- x BZT] perovskite solid solutions synthesized under high pressure was studied in situ via X-ray diffraction and piezoresponse force microscopy. The as prepared ceramics show a morphotropic phase boundary (MPB) between the non-polar orthorhombic and ferroelectric tetragonal states at 75 mol. % BZT. It is shown that annealing above 573 K results in irreversible changes in the phase diagram. Namely, for compositions with 0.2 < x < 0.6, the initial orthorhombic phase transforms into a ferroelectric rhombohedral phase. The new MPB between the rhombohedral and tetragonal phases lies at a lower BZT content of 60 mol. %. The phase diagram of the BMT-BZT annealed ceramics is formally analogous to that of the commercial piezoelectric material lead zirconate titanate. This makes the BMT-BZT system promising for the development of environmentally friendly piezoelectric ceramics.