Achieving outstanding comprehensive performance with high piezoelectricity in CaBi₂Nb₂O₉-based high-temperature piezoelectric ceramics via multi-field coupling strategy

Aurivillius phase CaBi₂Nb₂O₉ (CBNO) ceramic with an ultrahigh Curie temperature (T_C) of ∼934 °C shows huge potential in high-temperature piezoelectric applications. However, low piezoelectricity and poor electric insulation prevent its applications in high-temperature sensing. Here, we propose an effective multi-field coupling strategy to synergistically optimize piezoelectric property, electrical conduction behavior and temperature stability of CBNO ceramic. The constructed lattice stress and electric fields induced by introducing Li/Pr and Bi/Sc doping have great impacts on the lattice structure, microstructure, domain structure and defect chemistry. Therefore, a significant increase in piezoelectric activity (d₃₃) is resulted from the enhancement of polarization, the improvement of breakdown electric field and the production of nanoscale domains. In especial, the existence of pseudo-tetragonal phase boundary is helpful for the enhanced d₃₃. In the designed Ca_1–3x (Li_0.5Pr_0.5)_xBi_2+2xNb_2–xSc_xO₉ system, a high d₃₃ of ∼18.2 pC/N accompanied by an ultrahigh T_C of ∼938 °C is achieved in the x = 0.02 ceramic. This combined with high electrical resistivity (ρ∼1.72 MΩ⋅cm at 600 °C) and nearly stable d₃₃ (up to 800 °C) indicates that it is a very promising piezoelectric material for high-temperature (up to 600 °C or higher) sensing applications.