Electrical properties of a Cr 2 O 3 -modified Na 0.5 Bi 4.5 Ti 4 O 15 -Na 0.5 Bi 0.5 TiO 3 composite ceramic

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Electrical properties of a Cr2O3-modified Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 composite ceramic Weifeng Wu 1 & Yuxuan Han 1 & Xuan Huang 1 & Juan Du 2 & Wangfeng Bai 3 & Fei Wen 1 & Wei Wu 1 & Peng Zheng 1 Liang Zheng 1 & Yang Zhang 1

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Received: 19 March 2020 / Revised: 9 October 2020 / Accepted: 13 November 2020 # Australian Ceramic Society 2020

Abstract 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 Cr2O3modified 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. Keywords Na0.5Bi4.5Ti4O15-Na0.5Bi0.5TiO3 . Cr2O3 . Composite ceramics . Piezoelectric properties . Electrical resistivity

Introduction Bismuth layer-structured ferroelectric ceramics are quite attractive to researchers because of their high Curie temperatures, low dielectric constants, low aging rate, low temperature coefficients of resonant frequency, and strong anisotropic electromechanical coupling factors [1–5]. However, lower piezoelectric activity is still an Achilles’ heel that limits its practical application. To improve the piezoelectric activity of the ceramics, many studies have been conducted in which ion doping technology * Peng Zheng [email protected] 1

Lab for Nanoelectronics and NanoDevices, Department of Electronics Science and Technology, Hangzhou Dianzi University, Hangzhou 310018, China

2

School of Materials Sciences and Engineering, Liaocheng University, Liaocheng 252059, China

3

College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018, China

has been the most commonly used method. Several bismuth layer-structured ceramics with high piezoelectric activities have been obtained using this strategy [6–14]. However, studies have shown that in Pb(Zr,Ti)O3 (PZT), Na0.5Bi0.5TiO3 (BNT), and K0.5Na0.5NbO3 (KNN), the construction of mul