Electrical properties of a Cr2O3-modified Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 composite ceramic.

In this work, Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 and Cr2O3-modified Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 composite ceramics were fabricated and investigated as potential candidates for high-temperature piezoelectric applications. The microstructure, phase structure, and resulting piezoelectric properties of the ceramics were studied in detail. The coexistence of bismuth layer-structured ((Bi2O2)2+(Am−1BmO3m+1)2−) and perovskite structured (ABO3) phases was confirmed by X-ray diffraction analysis. The volume fraction ratio of pristine Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 was determined to be 84.3:15.7, while that of the Cr2O3-modified one was 85.9:14.1, which agreed well with the theoretical value. Following doping, a small amount of Cr3+ ions was diffused into the crystal lattices of both phases, promoting the grain growth and resulting in a slight increase of the Curie temperature TC from 656 to 658 °C. Moreover, optimized piezoelectric properties with a significant piezoelectric constant d33 of 25 pC/N and a stable thermal annealing behavior were achieved in this ceramic. In addition, compared with the pure composite ceramic, the Cr2O3-modified composite ceramic exhibited a higher resistivity of 0.04 MΩ·cm at 600 °C. These results demonstrated the potential of the Cr2O3-modified Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 composite ceramic in high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]