Achieving ultra-high resistivity and outstanding piezoelectric properties by co-substitution in CaBi2Nb2O9 ceramics

CaBi₂Nb₂O₉ (CBNO) ceramics exhibit significant potential in the development of piezoelectric sensors suitable for extreme environments such as aerospace, metallurgy, and nuclear power plants. While previous studies have enhanced the piezoelectric response of CBNO ceramics, their insulating properties at high temperatures still require improvement. In this work, co-substitution of (Li_0.5Bi_0.5) at A site and Mn at B site was designed to improve the electrical properties of CBNO ceramics. Defect dipoles induced by the bound between Mn and oxygen vacancies restrict the movement of oxygen vacancies at high temperatures. Meanwhile, co-substitution of Ca by (Li_0.5Bi_0.5) reduces both the sintering temperature and volatilization of Bi₂O₃ during the sintering process. This modification results in an ultra-high T_C of 928 °C and an exceptional resistivity of 2.85 MΩ·cm at 600 °C for Ca_0.96(Li_0.5Bi_0.5)_0.04Bi₂Nb_1.98Mn_0.02O₉ ceramics. Furthermore, the ceramic exhibits excellent piezoelectric properties (d₃₃ of 15.2 pC/N and k_p of 6.9%), ferroelectric properties (P_r of 9.42 μC/cm²), and thermal stability (degeneration of d₃₃ only 6% after annealing at 900 °C for 2 h). This work offers a practical strategy for simultaneously achieving both a high piezoelectric response and outstanding insulating properties in the CBNO system.