ELECTRICAL-PROPERTIES OF LAYER-STRUCTURED PB2BI4TI5O18 SINGLE-CRYSTALS

Single crystals of lead bismuth titanate (Pb2Bi4Ti5O18) were grown and their electrical properties were investigated by measuring the dielec tric permittivity, conductivity and spontaneous polarization. The diel ectric permittivity, measured at 1 MHz, was 10400 in the direction par allel to the bismuth layer (crystallographic a(b)-axis) at the Curie t emperature of 340 degrees C. This value was about 30 times higher than that in the perpendicular direction (crystallographic c-axis). The DC conductivity was about two orders of magnitude higher in the directio n parallel to the bismuth layer than that in the perpendicular directi on at 200 to 500 degrees C. A large anisotropy of the ferroelectricity was observed in D-E hysteresis curves at 150 degrees C, and the exist ence of spontaneous polarization in the c-axis direction was experimen tally confirmed, though it was much smaller than that in the a(b)-axis direction. Among the bismuth layer-structured ferroelectrics, Pb2Bi4T i5O18 in the a(b)-axis direction was found to have a low coercive fiel d and a large remanent polarization.