Enhancement of the piezoelectric and ferroelectric properties of CaBi2Nb2O9 ceramics by optimizing excess Bi2O3

Calcium bismuth niobate (CaBi 2 Nb 2 O 9 , CBNO) piezoelectric ceramics are promising materials for high-temperature sensors, actuators, and transducers. However, the unique layered structure of CBNO typically results in a low piezoelectric response. Previous studies have generally improved their electrical properties through complex ion substitution or preparation process optimization. Nonetheless, bismuth oxide (Bi 2 O 3 ) volatilization during sintering remains an inevitable issue. This leads to Bi vacancies, oxygen vacancies, and non-stoichiometric composition, negatively affecting both electrical performance and structural stability. In this work, we focus on the influence of excess Bi 2 O 3 on defect compensation and electrical properties. The ceramic with 2 % excess Bi 2 O 3 exhibits ultra-high T C of 929 °C, high d 33 of 14.1 pC/N, 2 P r of 25.5 μC/cm 2 , excellent ρ of 1.02 × 10 5  Ω cm at 600 °C, as well as excellent thermal stability with the d 33 remaining 13.3 pC/N (less than 6.0 %) after annealed at 800 °C for 2 h. This strategy offers a practical solution to improve the stability and performance of CBNO ceramics for high-temperature applications.