The phase diagram of K_0.5Na_0.5NbO₃-Bi_1/2Na_1/2TiO₃

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• 作者：Laijun Liu ; Michael Knapp ; Helmut Ehrenberg ; Liang Fang ; Ljubomira Ana Schmitt ; Hartmut Fuess ; Markus Hoelzel and Manuel Hinterstein
• 关键词：K0.5Na0.5NbO3 ; Bi1/2Na1/2TiO3 ; phase diagrams ; morphotropic phase boundaries ; polymorphic phase boundaries
• 刊名：Journal of Applied Crystallography
• 出版年：2016
• 出版时间：April 2016
• 年：2016
• 卷：49
• 期：2
• 页码：574-584
• 全文大小：1513K
• ISSN：1600-5767

文摘

The phase diagram of the lead-free piezoelectric (1 − x)K_0.5Na_0.5NbO₃–xBi_1/2Na_1/2TiO₃ system has been studied by high-resolution synchrotron powder diffraction, neutron powder diffraction and selected area electron diffraction. The two lead-free piezoelectric materials K_0.5Na_0.5NbO₃ and Bi_1/2Na_1/2TiO₃ form an infinite substitution solid solution. The orthorhombic (O), monoclinic (M), tetragonal (T) and rhombohedral (R) phases and the phase coexistence of M (Pm) + T (P4mm) for 0.02 < x ≤ 0.14, T (P4bm) + pseudocubic () for 0.14 < x ≤ 0.87 and T (P4bm) + R (R3c) for 0.87 < x ≤ 0.96 have been investigated at room temperature, with a subtle change in the structure observed. The oxygen octahedral tilt system has been mapped as a function of composition and temperature. The results indicate that K_0.5Na_0.5NbO₃–Bi_1/2Na_1/2TiO₃ does not display a morphotropic phase boundary like lead zirconate titanate, and that the most significant structural changes as a function of composition occur near x = 0.14 and x = 0.87 as a result of ionic disorder at the A and B sites in the perovskite ABO₃ structure at room temperature.