Large Strain Response in 0.99(Bi0.5Na0.4K0.1)TiO3-0.01(KxNa1−x)NbO3 Lead-Free Ceramics Induced by the Change of K/Na Ratio in (KxNa1−x)NbO3

• Published in: Journal of the American Ceramic Society 2013-10, Vol.96 (10), p.3133-3140
• Main Authors: Hao, Jigong, Shen, Bo, Zhai, Jiwei, Liu, Chunze, Li, Xiaolong, Gao, Xingyu
• Format: Article
• Language: English
• Subjects: Ceramics; Ergodic processes; Ferroelectric materials; Ferroelectricity; Phase boundaries; Phase transformations; Relaxors; Strain
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.12462

Influence of K/Na ratio in (KxNa1−x)NbO3 on the ferroelectric stability and consequent changes in the electrical properties of 0.99(Bi0.5Na0.4K0.1)TiO3–0.01(KxNa1−x)NbO3 (BNKT–KxNN) ceramics were investigated. Results showed that change of K/Na ratio in KNN induces a phase transition from ferroelectric to ergodic relaxor phase with a significant disruption of the long‐range ferroelectric order, and correspondingly adjusts the ferroelectric–relaxor transition point TF−R to room temperature. Accordingly, giant strain of ~0.46% (corresponding to a large signal d33* of ~575 pm/V) which is comparable to that of Pb‐based antiferroelectrics is obtained at a K/Na ratio of ~1, and the emergence of large strain response induced by the change of K/Na ratio of KNN can be well explained by the correlation between the position of ferroelectric–ergodic relaxor phase boundary in the BNKT–KxNN system and the tolerance factor t of the end number (KxNN). In situ high‐energy X‐ray scattering experiments with external field reveals that the large strain response in the studied system is likely related to the electric field‐induced distortion from the pseudocubic structure.