High‐performance bismuth titanate‐ferrite (Bi <sub>5</sub> Ti <sub>3</sub> FeO <sub>15</sub> ) for high‐temperature piezoelectric applications
Qian Wang, En‐Meng Liang, Chun‐Ming Wang
Abstract
Abstract Advancing the development of high‐temperature piezoelectric sensors requires high‐performance piezoelectric materials with high Curie temperatures, wherein the charge signals can be efficiently collected at elevated temperatures. The bismuth layer‐structured ferroelectric (BLSF) bismuth titanate‐ferrite (Bi 5 Ti 3 FeO 15 , BTF) has recently attracted considerable attention because of its high Curie temperature ( T C ) of ∼761°C. However, the piezoelectric properties of BTF‐based compounds have not been extensively investigated because of their extremely poor piezoelectric performances and low electrical resistivities at elevated temperatures. Herein, tungsten‐substituted BTF (BTF‐100 x W) ceramics were synthesized using a solid‐state reaction method. X‐ray diffraction refinement results confirmed the lattice distortion of the B O 6 octahedron, while piezoelectric force microscopy images verified an increase in the domain wall density with tungsten modification, both of which contribute to significant enhancement of the piezoelectric properties of BTF‐100 x W as intrinsic and extrinsic contributions, respectively. Remarkably, BTF‐3W exhibits a high T C of 793°C and a large piezoelectric constant ( d 33 ) of 24.3 pC/N, which is over three times that of BTF (7.1 pC/N). Importantly, the substitution of tungsten decreases the concentration of oxygen vacancies, increases the direct current electrical resistivity, and improves the electrical homogeneity at high temperatures, resulting in extremely stable piezoelectric and electromechanical properties at high temperatures, with a high in‐situ relative d 33 of >90% at 400°C and a small variation in the electromechanical coupling factor ( k p ) of <8% at temperatures up to 450°C. These results suggest that the tungsten‐substituted BTF is a potential candidate for high‐temperature piezoelectric ceramics, and is a promising material for applications in high‐temperature piezoelectric sensors.