New high Tc piezoelectric ceramics with bismuth layer structure

The systematic investigation of the composition and structure of high T-c piezoelectric materials with bismuth layer structure was carried out. It was shown that a new kind of piezoelectric ceramics with the Curie temperature more than 850degreesC can be obtained by non-stoichiometric amount compound substitution of CaBi4Ti4O15-based (CBT based) ceramics. The increase of the Curie temperature is due to the change of the phase transition energy caused by the structural distortion. The electrical properties and their high temperature stability of the modified CBT based ceramics also were investigated from the point of view of its application as a high temperature piezoelectric material. The new material with a bismuth layer structure has the following properties: T-c>850degreesC, d(33)=18x10(-12)C/N, epsilon(33)(T)/epsilon(0)=130, TKC(500degreesC)<10x10(-4)/°C, ρ(v)(500°C)>2x10(7)Omega.cm.