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 dielectric permittivity, conductivity and spontaneous polarization. The dielectric permittivity, measured at 1 MHz, was 10400 in the direction parallel to the bismuth layer (crystallographic a(b)-axis) at the Curie temperature 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 direction parallel to the bismuth layer than that in the perpendicular direction 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 existence of spontaneous polarization in the c-axis direction was experimentally confirmed, though it was much smaller than that in the a(b)-axis direction. Among the bismuth layer-structured ferroelectrics, Pb2Bi4Ti5O18 in the a(b)-axis direction was found to have a low coercive field and a large remanent polarization.