Phases and morphotropic regions in the PbNb2/3 Mg1/3O3-PbTiO3 system

Ceramic samples of solid solutions (1 − x ) PbNb 2/3 Mg 1/3 O 3 · x PbTiO 3 (0 ≤ x ≤ 1.0, Δ x = 0.0025–0.05) are prepared by the columbite method. A detailed x − T phase diagram of the system is constructed (isothermal join at 25°C), and dielectric, piezoelectric, and elastic properties are investigated. It is established that the region of the morphotropic phase transition is positioned in the range 0.28 < x ≤ 0.43 and consists of a series of narrower regions. Inside one phase (cubic, rhombohedral, tetragonal), regions are found in which a qualitative and quantitative difference in structural and electrical parameters is observed. An interpretation of the observed effects in the context of the defect structure of the objects is suggested.