EFFECTS OF DC BIAS FIELDS ON DIELECTRIC-PROPERTIES AND PHASE-TRANSITION BEHAVIOR OF THE (1-X)[PB0.7BA0.3)(MG1/3NB2/3)O3]-XPBTIO3 SYSTEM OF MORPHOTROPIC PHASE-BOUNDARY COMPOSITIONS

Abstract

The effect of DC bias on the dielectric properties and the phase transition behaviour of the (1 - x) [(Pb0.7Ba0.3) (Mg1/3Nb2/3)O3]-xPbTiO3 ceramic system near the morphotropic phase boundary (0.35 less-than-or-equal-to x less-than-or-equal-to 0.5) have been investigated. The phase transition goes through a series of character changes from being a diffuse phase transition at x = 0.35 to being a more or less normal phase transition at x = 0.5. Between the extreme compositions, the system has shown a rather anomalous phase transition behaviour due to the existence of the morphotropic phase boundary centred around x = 0.44. On subjection to a series of external biases, the averaged dielectric constant maximum temperatures of the specimens of intermediate compositions tend to oscillate with respect to the bias field. Such anomalous dielectric behaviour is ascribed to the coexistence of multiple phases in a narrow composition band whose centre of gravity may be assigned as the morphotropic phase boundary.