Phase relations in the system of (Na1/2Bi1/2)TiO3-PbTiO3 .2. Dielectric property

The region of the phase diagram in the system (Na1/2Bi1/2)(1-x)PbxTiO3 from x = 0 to 0.2 was established using dielectric measurements along with the phase diagram established in part I of this work. The diffuse phase transition behavior of solid solutions with low PbTiO3 content was also investigated. When x is lower than x(rc) (composition at which rhombohedral <----> cubic transition exists) the rhombohedral <----> tetragonal transition accompanied an anomaly in the epsilon(T) curve which shows an abrupt jump, followed by diffuse behavior of the epsilon(T) curve during heating. When x(rc) < x < x(MPB) (rhombohedral-tetragonal morphotropic phase boundary composition at room temperature) the rhombohedral <----> tetragonal transition was a normal ferroelectric-to-ferroelectric transition but the tetragonal <----> cubic transition showed diffuse behavior following the abrupt jump in the epsilon(T) curve. The temperature of the structural change coincided with the abrupt jump in epsilon(T) curve. Normal ferroelectric phase transition from ferroelectric tetragonal to paraelectric cubic was found when x > x(MPB). It was found that the temperature range of the reported antiferroelectric phase would follow that of the diffuse transition range regardless of the crystal symmetry. It can be said that the antiferroelectric phase of (Na1/2Bi1/2)(1-x)PbxTiO3 is strongly connected with the diffuse transition behavior during ferroelectric phase transition. (C) 1996 American Institute of Physics.