Electrical anisotropy in single crystals of Bi-layer structured ferroelectrics

Single crystals of PbBi2Nb2O9 (PBN), PbBi4Ti4O15 (PBT) and Pb2Bi4Ti5O18 (P2 BT), belonging to the bismuth layer-structured ferroelectric compound, were grown and dielectric, conducting and ferroelectic properties were evaluate d separately in directions of a(b)-axis and c-axis. The relationship betwee n crystal structure (the number of oxygen octahedra in the perovskite block m) and electrical properties was discussed comprehensively. The dielectric permittivity at T-c in the a(b)-axis direction was more than 20 times larg er than for the c-axis direction. The anisotropy depended on m and was larg er in the compound with even-number m than that with odd-number m. The DC c onductivity increased with increasing rn in both a(b)-axis and c-axis direc tions. The spontaneous polarization in the c-axis direction was not recogni zed for PEN and PET with even-number In but observed for P2BT with odd-numb er tla, although the value of remanent polarization was much smaller than f or the a(b)-axis direction. (C) 2000 Elsevier Science Ltd and Techna S.r.l. All rights reserved.