(1 − x)(K0.48Na0.52)(Nb0.95−y−zTazSby)O3–xBi0.5(Na0.82K0.18)0.5ZrO3 lead-free ceramics: composition dependence of the phase boundaries and electrical properties. Issue 10 (13th February 2015) - Lv, Xiang
Abstract : In this work, the KNNST-BNKZ- xyz ceramics were obtained, and the composition dependence of their phase structures and electrical properties was discussed. Abstract : In this work, (1 − x )(K0.48 Na0.52 )(Nb0.95− y − z Ta z Sb y )O3 - x Bi0.5 (Na0.82 K0.18 )0.5 ZrO3, {abbreviation: KNNST-BNKZ- x-y-z } lead-free piezoceramics were prepared by a conventional solid-state reaction method, and the composition dependence of their phase structures and electrical properties was systematically discussed. Doping with Sb 5+, Ta 5+, and BNKZ plays an important role on the phase boundaries as well as piezoelectric activity. A three-phase coexistence involving rhombohedral-orthorhombic-tetragonal (R–O–T) phases was observed in the ceramics with 0.0325 ≤ x ≤ 0.05, 0.035 ≤ x ≤ 0.065, 0.05 ≤ z ≤ 0.08, indicating that doping with BNKZ, Ta 5+, and Sb 5+ can induce the formation of such a phase boundary by simultaneously increasing T R–O and decreasing T O–T . Enhanced piezoelectric behavior was observed in the ceramics located in the composition region of the R–O–T phase boundary, and a high d 33 value of 400 pC N −1 can be attained by refining their compositions ( e.g., x = 0.0325, y = 0.035, and z = 0.05), together with a high T C value of ∼240 °C. Of particular interest is that a large electric field-induced strain of 0.18% ( S max / E max = 706 pm V −1 ) was also found in the ceramics with x = 0.0325, y = 0.035, and z = 0.05 under a low electric field of 2.5 kV mm −1 . As a result, the piezoelectric activity as well as the strain can be operated in the material system by refining x, y, and z content.