DIELECTRIC-PROPERTIES AND PHASE-TRANSITION OF 0.5[(1-X)PBYB1 2NB1/2O3-XPBTIO(3)]-0.5PBZRO(3) SOLID-SOLUTION/

The phase diagram of the 0.5[(1-x)PbYb1/2Nb1/2O3-(x)PbTiO3]-0.5PbZTO(3 ) ceramic system has been determined. A typical relaxer ferroelectric behavior with field dependent hysteresis loops in 0.5PbYb(1/2)Nb(1/2)O (3)-0.5PbZrO(3) (x = 0) was observed. As the PbTiO3[PT] content increa ses, however, the relaxor behavior abruptly disappears. The phase at r oom temperature is a relaxer between a = 0 and 0.1; a pseudocubic ferr oelectrics (FE) between a: = 0.1 and 0.4, a rhombohedral FE between x = 0.5 and 0.9 and a tetragonal FE between a: = 0.9 to 1.0. In particul ar, a morphotropic phase boundary is found to exist between the rhombo hedral and tetragonal FE phases in the vicinity of x = 0.9.