Average vs. local structure and composition-property phase diagram of K_0.5Na_0.5NbO₃-Bi_½Na_½TiO₃ system

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• 作者：Laijun Liu^a ; ^b ; ^{ljliu2@163.com} ; Michael Knapp^a ; Helmut Ehrenberg^a ; Liang Fang^b ; Huiqing Fan^c ; Ljubomira Ana Schmitt^d ; Hartmut Fuess^d ; Markus Hoelzel^e ; Hichem Dammak^f ; Mai Pham Thi^g ; Manuel Hinterstein^a ; ^h
• 关键词：Structure ; Dielectric relaxation ; Phase diagram ; Lead-free ceramics
• 刊名：Journal of the European Ceramic Society
• 出版年：2017
• 出版时间：April 2017
• 年：2017
• 卷：37
• 期：4
• 页码：1387-1399
• 全文大小：4179 K
• 卷排序：37

文摘

Phase diagram of the solid solution system K0.5Na0.5NbO3- Bi½Na½TiO3 [(1-x)KNN-xBNT] has been established from dielectric permittivity measurement and structure analyses. The unit cell volumes continuously decrease depending on the composition, while the local structure maintains distortions away from the cubic average structure in the range 0.10 ≤ x ≤ 0.90. No clear correspondence for the temperatures of phase transition exists between structural studies and physical properties. The dielectric behavior is depicted successively from normal ferroelectric, diffuse phase transition, re-entrant-like relaxor, relaxor + dipolar glass-like relaxor, BNT-like relaxor with the increase of BNT. A comprehensive composition-property phase diagram for this system has been given to understand the various ferroelectric phenomena. The result could be mainly elucidated by the nanoclusters and the disorder driven nucleation of polar nanoregions contributed by a valence mismatch at one of the cation sites.