Structure evolution and piezoelectric properties of K0.40Na0.60Nb0.95Sb0.05O3–Bi0.5K0.5HfO3–SrZrO3 ternary lead-free ceramics with R–O–T phase boundary

• Published in: Journal of materials science. Materials in electronics Vol. 32; no. 7; pp. 9032 - 9043
• Main Authors: Liu, Yunyi, Pan, Yongqi, Bai, Xudong, Wang, Jinchuan, He, Caiwang, Xu, Zunping, Chen, Yi
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.04.2021; Springer Nature B.V
• Subjects: Ceramics; Characterization and Evaluation of Materials; Chemistry and Materials Science; Coupling coefficients; Crystal structure; Grain growth; Lead free; Materials Science; Niobates; Optical and Electronic Materials; Phase boundaries; Phase transitions; Piezoelectricity; Strontium zirconates
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-021-05573-7

A conventional ceramic preparation method was used to fabricate the newly designed ternary (K,Na)NbO 3 -based lead-free ceramics, which have the general formula of (0.97- x )K 0.40 Na 0.60 Nb 0.95 Sb 0.05 O 3 –0.03Bi 0.5 K 0.5 HfO 3 – x SrZrO 3 . An X-ray diffraction analysis, together with dielectric-temperature measurements, was performed for determining their phase structures. The crystal structure was found to transition from a rhombohedral-orthogonal phase coexistence to a three-phase coexistence of rhombohedral-orthogonal-tetragonal phases with the increase in SrZrO 3 concentration, and then to a rhombohedral-tetragonal phase coexistence, and finally to a single rhombohedral phase. Near the three-phase coexistence zone, the ceramics exhibit an obviously enhanced electrical activity, with an electromechanical coupling coefficient k p  = 0.364 and a piezoelectric constant d 33  = 280 pC/N. Through a microstructure analysis, a slightly excessive amount of SrZrO 3 was found to result in an inhibition for the grain growth of the studied ceramics. These results show that incorporating SrZrO 3 into ternary (K,Na)NbO 3 -based ceramics is still an effective means of constructing phase boundaries and improving the electromechanical properties.