Greatly improved piezoelectricity and thermal stability of (Na, Sm) Co-doped CaBi2Nb2O9 ceramics

Abstract

Calcium bismuth niobate (CaBi2Nb2O9) is regarded as one of the most potential high-temperature piezoelectric materials owing to its highest Curie point in bismuth layer-structured ferroelectrics. Nevertheless, low piezoelectric coefficient and low resistivity at high temperature considerably restrict its development as key electronic components. Herein, markedly improved piezoelectric properties and DC resistivity of CaBi2Nb2O9 ceramics through Na+ and Sm3+ co-doping are reported. The nominal compositions Ca1-2x(Na, Sm)xBi2Nb2O9 (x ​= ​0, 0.01, 0.025, and 0.05) ceramics have been prepared via the conventional solid state method. An optimum composition of Ca0.95(Na, Sm)0.025Bi2Nb2O9 is obtained, which possesses a high Curie point of ∼949 ​°C, a piezoelectric coefficient of ∼12.8 ​pC/N, and a DC electrical resistivity at 500 ​°C of ∼4 ​× ​107 ​Ω ​·cm. The improved d33 is probably ascribed to the reduction in domain size and the increase in domain wall density caused by the reduced grain size. More importantly, after annealing at 900 ​°C for 2 ​h, the piezoelectric coefficient still maintains about 90% of the initial d33 value, which displays a significant improvement compared to pure CaBi2Nb2O9 ceramic with only 44% of the initial d33 value. This work exhibits a feasible approach to simultaneously obtain high piezoelectric property and thermal stability in CaBi2Nb2O9 ceramics by Na+/Sm3+ co-doping.

Keywords

• High-temperature piezoceramics
• CaBi2Nb2O9
• A-site co-doping
• Piezoelectric performance
• Thermal stability