Origin of strong piezoelectric enhancement in bismuth titanate‐ferrite for high‐temperature applications

Abstract

Advancing the development of high‐temperature piezoelectric devices requires high‐performance piezoelectric materials with high Curie temperature, where charge signals can be efficiently collected at elevated temperatures. Recent investigations indicate that bismuth titanate‐ferrite (Bi5Ti3FeO15) is a good high‐temperature piezoelectric material because of its high Curie temperature (TC > 760°C). However, the piezoelectric performance of Bi5Ti3FeO15‐based compounds has not been extensively studied because of their extremely poor piezoelectric performance and low direct current electrical resistivity at elevated temperatures. Herein, we reported the strong piezoelectric performance enhancement in Bi5Ti3FeO15, with the nominal compositions of Bi5‐xEuxTi3FeO15 (BTF‐100xEu). X‐ray diffraction Rietveld refinements and Raman spectra reveal an enhanced lattice distortion in europium‐substituted Bi5Ti3FeO15, which is mainly dominated by rotation distortion. The increased domain wall density that detected by out‐of‐plane piezoelectric force microscopy is in favor of domain wall movement and polarization reversal. Both of the enhanced lattice distortion and the increased domain wall density contribute to the piezoelectric enhancement in Bi5Ti3FeO15, as a result, the optimal composition of BTF‐8Eu exhibits a large piezoelectric constant d33 of 24 pC/N, three times higher than that of Bi5Ti3FeO15. Importantly, BTF‐8Eu exhibits high TC of 782°C, excellent in‐situ piezoelectric response (>94% that of the initial value at room temperature), and stable electromechanical coupling properties up to 400°C. This work reveals the origin of strong piezoelectric enhancement in europium‐substituted Bi5Ti3FeO15 results from the intrinsic contribution of structure distortion and the extrinsic contribution of ferroelectric domain.