Study on A-site Cation Doping of CaBi2Nb2O9 with Bismuth Layered Structure

High curie temperature piezoelectric ceramics based on KLa-dopedCa1-x(KLa)x/2Bi2Nb2O9(x=0–0.20) were prepared by a conventional solid state reaction method. Crystal structure and microstructures of Ca1-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+(Am-1BmO3m+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 ofCa1-x(KLa)x/2Bi2Nb2O9 ceramics shows that all of them have a high Curie point (Tc≥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, Tc=870 nd 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.