X-RAY AND DIELECTRIC STUDIES OF THE PHASE-TRANSITIONS IN PB(YB1/2NB1/2)O-3-PBTIO3 CERAMICS

Phase analysis and dielectric measurement have been conducted for a comprehensive study of the phase transition in the whole composition range of (1 - x)Pb(Yb1/2Nb1/2)O-3-xPbTiO(3) (PYN-PT) ceramic system. For all compositions, a continuous series of complete solid solutions of the antiferroelectric (AFE) and the ferroelectric (FE) compounds was found. With increasing PT concentration x, the phase transition in this system can be categorized as three distinct classes in connection with the degree of the structural ordering. The PYN-rich solutions showed a relatively sharp first-order paraelectric (PE)-AFE transition behavior and the transition temperature decreases rapidly with increasing x. For 0.10 < x < 0.25, the phase transition is broadened and frequency-dependent. Beyond x = 0.25, the normal PE-FE phase transition was observed and the transition temperature increases rapidly with increasing x. In the FE side, it was also revealed that the morphotropic phase boundary between pseudocubic and tetragonal structure lies in the vicinity of x = 0.5. Moreover, the resultant phase diagram with temperature and PT concentration is presented.