Enhancement of piezoelectric properties with high Curie temperature in CaBi2Nb2O9 via MnO2 doping

MnO 2 -doped Ca 0.97 Bi 2.03 Nb 2 O 9 ceramics with greatly improved piezoelectric performance were prepared via conventional solid state sintering method. The effects of MnO 2 doping on the microstructure and electrical properties of Ca 0.97 Bi 2.03 Nb 2 O 9 ceramics were studied. X-ray diffraction (XRD) analysis and Rietveld refinement revealed a reduction in orthorhombicity with MnO 2 doping, which contributed to the enhancement of the piezoelectric properties. Furthermore, the introduction of MnO 2 lowered the sintering temperature, thereby reducing the formation of oxygen vacancies in the ceramic. The optimal performance was achieved in the Ca 0.97 Bi 2.03 Nb 2 O 9 −0.3wt.%MnO 2 sample, exhibiting a piezoelectric coefficient ( d 33 ) of 13.6 pC/N, a DC resistivity of 3×10 6 Ω·cm at 500 °C, and a Curie temperature of 965 °C. Additionally, all doped samples demonstrated excellent thermal stability over a wide temperature range, from room temperature to 900 °C.