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

Calcium bismuth niobate (CaBi 2 Nb 2 O 9 ) 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 CaBi 2 Nb 2 O 9 ceramics through Na + and Sm 3+ co-doping are reported. The nominal compositions Ca 1-2 x (Na, Sm) x Bi 2 Nb 2 O 9 ( x ​= ​0, 0.01, 0.025, and 0.05) ceramics have been prepared via the conventional solid state method. An optimum composition of Ca 0.95 (Na, Sm) 0.025 Bi 2 Nb 2 O 9 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 ​× ​10 7 ​Ω ​·cm. The improved d 33 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 d 33 value, which displays a significant improvement compared to pure CaBi 2 Nb 2 O 9 ceramic with only 44% of the initial d 33 value. This work exhibits a feasible approach to simultaneously obtain high piezoelectric property and thermal stability in CaBi 2 Nb 2 O 9 ceramics by Na + /Sm 3+ co-doping. Calcium bismuth niobite (CaBi 2 Nb 2 O 9 ) is the bismuth layered structure ferroelectric with the highest Curie temperature, however, its piezoelectric coefficient d 33 is extremely low. Na and Sm co-doping at A site are used to modify it, and its piezoelectric properties and thermal stability are significantly improved.