Structures and Properties of Bismuth Layer-structured Piezoelectric Ceramics with High T_c

This paper reviewed the structures and properties of bismuth layer--structured piezoelectric ceramics. The structures of bismuth layer-structured piezoelectric ceramics are built up by the regular intergrowth of (Bi2O2)2+ layers and perovskite (Am-1BmO3m+1)2- slabs where A is a combination of canons adequate for 12-coordinated interstices, B is a combination of cations well suited to octahedral coordinated, and m is an integer usually lying to the range 1-5. By comparison with barium titanate (BaTiO3) or lead zirconate titanate (PZT) ceramics, the bismuth layer-structured piezoelectric ceramics airs characterized by: (1) lower dielectric constant; (2) higher Curie temperature; (3) stronger anisotropy in electromechanical coupling factors; (4) lower ageing rate; (5) higher resistivity; etc.. Previous studies showed that Curie temperature depends on atomic displacement of polarization canons, spontaneous polarization, bismuth content in the cubooctahedral cavities, and the nature of the substituting canons such as inonic radius, electronegativities and electronic configuration. An essentially weak point of bismuth layer-structured piezoelectric ceramics is low piezoelectric activity which can be solved by chemical substitution or fabrication methods for orientating the grains in ceramics. It is necessary to study the relationships between structures and properties of bismuth layer-structured piezoelectric ceramics in order to develop the materials.