Evolution of crystallographic grain orientation and anisotropic properties of (K_0.5Na_0.5)NbO₃ ceramics using BaTiO₃ templates by reactive templated grain growth

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• 作者：Danya Lv ; Ruzhong Zuo ; ^{piezolab@hfut.edu.cn}
• 关键词：Platelike BaTiO3 particle ; Reactive templated grain growth ; Textured ceramics
• 刊名：Journal of Alloys and Compounds
• 出版年：2013
• 出版时间：25 May, 2013
• 年：2013
• 卷：560
• 期：Complete
• 页码：62-66
• 全文大小：646 K

文摘

Platelike BaTiO₃ (BT) templates were used for the first time to fabricate (0 0 1) textured K_0.5Na_0.5NbO₃ (KNN) piezoelectric ceramics. Plakelike BT templates with a thickness of 1-1.5 ¦Ìm and a mean diameter of 10-15 ¦Ìm were synthesized by the topochemical microcrystal conversion method using Bi₄Ti₃O₁₂ as precursor particles. A systematic investigation was conducted on illustrating the texture development and microstructure evolution as a function of heat-treatment conditions. It was found that the KNN-BT solid solution was formed between BT templates and matrix materials. The increase of sintering temperature and time induced an orthorhombic-tetragonal phase transition. And it was indicated that the dominant mechanism of texture development could be the abnormal grain growth in the textured KNN ceramics. A (0 0 1) orientation degree of 80 % was achieved at 1130 ¡ãC for 24 h. The textured ceramics showed anisotropic electrical properties in the direction of parallel and perpendicular to the casting plane. The orthorhombic-tetragonal polymorphic phase transition T_o-t, the tetragonal-cubic ferroelectric phase transition T_C, the dielectric constant ¦Å_r and the remnant polarization P_r values for the perpendicular cut specimens were lower than the parallel cuts. The excellent electric properties at the parallel cuts were found to be the dielectric constant ¦Å_r = 810, the piezoelectric charge constant d₃₃ = 163 pC/N, and the electromechanical coupling factor k_p = 0.37.