Impact of crystal structure and defect on the electric properties in (LiCeY)-doped CaBi₂Nb₂O₉-based high-temperature piezoceramics

The Ca_1–2x(LiCe_0.5Y_0.5)_xBi₂Nb₂O₉ (CBNLCY-100x, x = 0–0.07) high-temperature ceramics were prepared by the conventional solid state reaction. The LiCeY substitution at A-site led an improvement of octahedral tilt angle in the a–c plane of CBNLCY-100x ceramics, which resulted in an enhanced piezoelectric constant. CBNLCY-6 ceramic with high Curie temperature (T_C = 940 °C) had a high piezoelectric coefficient (d₃₃) of 16.3 pC/N, even after annealing at 800 °C for 2 h, the d₃₃ value of CBNLCY-6 ceramic still remained 92.6% of its original value. Furthermore, the dc conduction mechanism of the ceramics was studied. The oxygen vacancies played an important role in dc conduction mechanism at low temperature and the main conduction mechanism at high temperature was intrinsic conduction. The resistivity of CBNLCY-100x ceramics got highest value at x = 0.01 and the resistivity of CBNLCY-1 ceramic enhanced one order of magnitude compared with undoped CaBi₂Nb₂O₉ ceramic. These results suggest that the CBNLCY-6 ceramic is a promising candidate material for ultra-high temperature applications.