[20p-PB1-1~10] 9.1 Dielectrics, ferroelectrics

▼ [20p-PB1-6] Optimization of conditions of the synthesis of textured (Bi_0.5K_0.5)TiO₃ piezoelectric ceramics by a reactive templated grain growth method

〇(D)Gopal Prasad Khanal¹, Sangwook Kim¹, Ichiro Fujii¹, Shintaro Ueno¹, Tohru Suzuki², Satoshi Wada¹ (1.Univ. of Yamanashi, 2.NIMS)

Keywords:Reactive templated grain growth method, Bismuth potassium titanate; (Bi0.5K0.5)TiO3, Grain-oriented ceramics

Bismuth potassium titanate (Bi_0.5K_0.5)TiO₃ (BKT) piezoelectric ceramic is one of the promising lead-free candidates piezoelectric system because of its relatively high Curie temperature (T_c~400^oC), high depolarization temperature (T_d~300^oC), and a relatively high piezoelectric constant d₃₃ of 125 pC/N. However, the d₃₃ value is not sufficient for practical actuators and the d₃₃ needs to be enhanced. Besides, BKT itself being the promising lead-free candidate, it is also important as end member for a variety of solid solutions like BKT-BaTiO₃, BKT-(Bi_0.5Na_0.5)TiO₃, BKT-BaTiO₃-(Bi_0.5Na_0.5)TiO₃, and so on. The grain-orientation imparted by the (001)/(100)-oriented BKT ceramics to the BKT-based solid solutions with crystal symmetry other than the tetragonal system could yield significant properties enhancement due to domain engineering. And, for the preparation of textured BKT ceramics, plate-like H_1.08Ti_1.73O₄.nH₂O (HTO) were used as template particles owing to their uniform-morphology with high aspect ratio. In this study, we focused on optimization of preparation conditions for the synthesis of (001)/(100) oriented BKT ceramics, using HTO-Bi₂O₃-KHCO₃ and HTO-TiO₂-Bi₂O₃-KHCO₃ reaction system. The matrix TiO₂ particles were used in the second reaction system beside the HTO template particles because the ratio of the matrix to the template particles strongly affects the grain orientation of the RTGG-processed ceramics.