Dielectric behaviour of high-pressure (1 - x)PbMg1/3Nb2/3O3-xPbAl1/2Nb1/2O3 ceramics

Dielectric properties of perovskite solid solutions in the (1 - x)PbMg1/3Nb2/3O3-xPbAl1/2Nb1/2O3 system synthesized under high pressure and high temperature were studied. It has been found that the dielectric response of the high-pressure ceramics with x < 0.2 changes from two-phase behaviour to a solely relaxor one when annealing at elevated temperatures. The dielectric response of the ceramics and its evolution are considered in terms of an ordering action of the high-pressure synthesis and the opposite effect of the annealing process. The peculiarities of dielectric characteristics indicate the morphotropic phase boundary in the system at about x = 0.2. The local symmetry of the polar regions at the ranges above and below the boundary is discussed