Structural and electrical properties of high Curie temperature Aurivillius phase composite ceramics with largely enhanced piezoelectricity

High performance piezoelectric ceramics with high Curie temperatures（TC） are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_（0.99-x_Bi6.99＋x（Li Mn）0.01 Nb Ti5O24（x = 0–0.8） were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value（x 〈 0.4）. Phase separation occurred when more A-site Ca^2＋ ions were replaced by Bi^3＋ ions. Nevertheless, all composite samples showed d_（33） values about 2 to 3 times of that of the constituent phase Ca Bi4Ti4O15 and Bi3 Ti NbO9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics.