Abstract: High curie temperature piezoelectric ceramics based on KLa-doped Ca_1-x(KLa)_x/2Bi₂Nb₂O₉(x=0–0.20) were prepared by a conventional solid state reaction method. Crystal structure and microstructures of Ca_1-x(KLa)_x/2Bi₂Nb₂O₉ ceramics were characterized by XRD and SEM. XRD patterns show that the crystal structures are a single phase of bismuth oxide layer structure having general formula (Bi₂O₂)²⁺(A_m-1B_mO_3m+1)^2- with m = 2. The grains of polished and thermally etched surfaces revealled a plate-liked morphology. The Curie point (Tc) decreases obviously whereas the piezoelectric activity of CBNO ceramics is significantly improved by the doping of potassium and lanthanum. The KLa-doped CBNO materials have an electrical conductivity value 1–2 orders of magnitude lower than undoped samples. The thermal depoling behavior of Ca_1-x(KLa)_x/2Bi₂Nb₂O₉ ceramics shows that all of them have a high Curie point (T_c≥850℃) and show good resistance to thermal depoling up to temperatures close to their Curie points. The results showed that the excellent properties is obtained in the ceramics with composition of x=0.1, i.e. d₃₃=15.8 pC/N, T_c=870℃ and the DC conductivity is one order of magnitude smaller than that of undoped CBNO. All the results suggest that the doped CaBi₂Nb₂O₉ is a potential material for high temperature sensor.

Key words: piezoelectric ceramics, modified, d₃₃, CaBi₂Nb₂O₉