Superior piezoelectricity and resistivity in CaBi2Nb2O9 high-temperature piezoelectric ceramics: synergy of structural distortion and weak texturing

Abstract

A high ferroelectric Curie temperature T_C, a large piezoelectric coefficient d₃₃ and resistivity at high temperatures are three virtues that must be considered for piezoelectric materials with potential applications in high temperature sensors. In this paper, the effect of the B₂O₃ sintering aid on the microstructural and electrical properties of CaBi₂Nb₂O₉ is comprehensively investigated. X-ray and neutron powder diffraction combined with Rietveld refinement demonstrate that a trace amount of B³⁺ can be incorporated into the Nb-sites in Nb–O octahedra resulting in an increase in the lattice distortion. The addition of B₂O₃ induces the preferential growth of grains along the c-axis, as confirmed by the corresponding (001) pole figure. The enhanced distortion degree of the Nb–O octahedra and microstructural grain orientation give rise to improvements in the ferroelectric and piezoelectric properties of CaBi₂Nb₂O₉. The polycrystalline sample with the addition of 0.25 wt% B₂O₃ can realize a large d₃₃ of 20.4 pC N⁻¹ and an ultra-high electrical resistivity of 1.4 × 10⁷ Ω cm (at 600 °C), while still retaining a high T_C of 958 °C. These properties are comparable to those of most piezoelectric single crystals used at high temperature. This work provides a cost-effective way to improve the ferroelectric and piezoelectric properties in high temperature piezoelectric ceramics.