ELECTRICAL ANISOTROPIES IN LAYER-STRUCTURED LEAD BISMUTH TITANATE SINGLE-CRYSTALS

Single crystals of lead bismuth titanate (PbBi4Ti4O15) were grown by t he vertical gradient freeze method. Electrical anisotropy of the cryst als was investigated by measuring dielectric permittivity, DC conducti vity, and complex impedance. The dielectric permittivity measured at 1 MHz was 18300 in the direction parallel to the bismuth layer (crystal lographic a(b) axis) at the Curie temperature of 570 degrees C. This v alue was about 43 times higher than that in the perpendicular directio n (c axis). The DC conductivity at 700 degrees C was about one order o f magnitude higher in the direction parallel to the bismuth layer than in the perpendicular direction. Results of complex impedance measurem ents suggest that the bismuth layer has a lower capacitance and a high er resistivity than those of the pseudo-perovskite blocks and shows pa raelectric character from a low temperature below T-c. Copyright (C) 1 997 Elsevier Science Ltd.