Abstract:

In recent years, there has been an urgent need for piezoelectric ceramic material capable of operating at temperatures of 450 ℃ and above, which serves as a piezoelectric sensing element in high-temperature piezoelectric vibration sensors. Bi₄Ti₃O₁₂ (BIT) is a piezoelectric ceramic with a high Curie temperature (T_C~650 ℃) within the family of bismuth-layered ferroelectric ceramics, making it a promising candidate for high-temperature applications. However, inherent low piezoelectric constant (d₃₃) and low high-temperature resistivity of pure phase BIT ceramics limit their application in such environments. This work used solid-phase reaction method to prepare BIT-based piezoelectric ceramics with substitutions at A-site by Ce ions and at B-site by W/Ta/Sb ions (BCTWTaS-100x, x=0-0.04). Effect of Ce doping on the structure and electrical properties of BIT-based ceramics was studied. Introduction of Ce ions induces lattice distortion and modifies domain structure of BIT-based ceramics, thereby enhancing their piezoelectric properties (with a d₃₃ of 37 pC/N at x=0.03). With doping concentration of ions increasing, relative displacement of oxygen atoms at apex of TiO₆ octahedra increases, resulting in increased lattice distortion within BIT-based ceramic. Furthermore, BCTWTaS-3 ceramics demonstrate a high T_C of 673 ℃ and high-temperature resistivity maintaining on the order of 10⁶ Ω·cm at 500 ℃. These ceramics also exhibit good thermal stability of d₃₃. Notably, after depolarization at 600 ℃ for 2 h, d₃₃ can still maintain over 85% of its initial value. These finds indicate that BCTWTaS-100x ceramics have great potential for application in high-temperature environments exceeding 450 ℃.

Key words: Bi₄Ti₃O₁₂, high Curie temperature, piezoelectric ceramic, lattice distortion