Papers by Keyword: KNbO3

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Authors: Takashi Yoshiguchi, Toshitaka Ota, Nobuyasu Adachi
Abstract: By the solution-dropping method imitating the growth of stalagmite in nature, piezoelectric KNbO3 crystal was prepared onto a substrate by dropping metastable K2NbO3F aqueous solution. The transformation from K2NbO3F to KNbO3 was accelerated by separately dropping H2O2 solution at the same time. Under the conditions of K2NbO3F concentration of 4.2×10-2 mol/l, H2O2 concentration of 9mol/l, dropping rate of 1.7ml/min, dropping time of 2 h, and substrate temperature of 20°C, KNbO3 crystals of 2 to 5μm and polycrystalline film composed of KNbO3 crystals of < 1μm were grown at aqueous temperatures of 20°C and 60°C, respectively.
Authors: Kiyotaka Tanaka, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: The development of lead-free piezoelectric materials has been required from the viewpoint of environmental preservation. We focused the lead-free KNbO3-based systems, and used a chemical solution deposition (CSD) process to obtain their precursor. (Na1-xKx)NbO3 precursor solutions were prepared from metal alkoxides and solvents such as absolute ethanol and 2-methoxyethanol. Crystallization behavior of the precursor gels obtained from the above solutions was investigated by the thermogravimetry differential thermal analysis (TG-DTA) measurement.
Authors: Kiyotaka Tanaka, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: Various KNbO3 powders have been derived from sol-gel process by using different preparation and heating conditions. KNbO3 powder derived from ethanol solution and fabricated at 800oC was most suitable as the raw material of KNbO3 bulk ceramics, because of the small grain size of about 250 nm and its homogeneous size distribution.
Authors: Kenichi Kakimoto, Izumi Masuda, Hitoshi Ohsato
Authors: Min Jin, Hui Shen, Jia Yue Xu
Abstract: In the present work, a pulling down method was introduced to prepare the KNbO3 crystals and the growth results were evaluated. It was found the Pt crucible with 60° cone angle and folds at the seed well was helpful to obtain KNbO3 crystal with nice integrity. The blue color occurred on the top of KNbO3 ingot was confirmed to be orthorhombic KNbO3 by XRD analysis. Some complex domain structures, including 60°, 90° and 180° domains, were happened in the crystal which were attributed to phase transitions when it was cooled down to room temperature.
Authors: Hiro Einishi, Mutsuo Ishikawa, Mitsumasa Nakajima, Sintaro Yasui, Tomoaki Yamada, Minoru Kurosawa, Hiroshi Funakubo
Abstract: KNbO3 thin films were deposited at 240 oC on various kinds of single crystal substrates by hydrothermal method using aqueous solutions containing Nb2O5 and KOH. The deposition amount of the films was found not to be much dependent on the orientation and the surface roughness of the substrates, but on the electrical conductivity of the substrate. Epitaxial {100}, {110} and {111}-oriented KNbO3 films with ferroelectricity were grown on (100)c, (110)c, and (111)c -oriented SrRuO3//(100)SrTiO3 substrates, respectively.
Authors: Kenichi Kakimoto, K. Higashide, Hitoshi Ohsato
Authors: Shigeki Sato, Yoji Noumura, Yuji Hiruma, Hajime Nagata, Tadashi Takenaka
Abstract: High-power piezoelectric characteristics of (Bi1/2Na1/2)TiO3 (BNT)- and KNbO3 (KN)-based ceramics at continuous driving were investigated. The selected compositions of BNT- and KN-based ceramics were 0.88(Bi1/2Na1/2)TiO3-0.04(Bi1/2Li1/2)TiO3-0.08(Bi1/2K1/2)TiO3 doped with 0.6 wt% MnCO3 [BNLKT4-8Mn0.6] and KNbO3-MnCO3 0.8 wt% [KN-Mn0.8] ceramics. It was found that the vibration velocity v0-P of BNLKT4-8Mn0.6 and KN-Mn0.8 ceramics linearly increased up to approximately 0.8 and 0.6 m/s, respectively. The temperature increases of BNLKT4-8Mn0.6 and KN-Mn0.8 ceramics were approximately 5°C under continuous driving at the vibration velocity of 0.6 m/s.
Authors: Takafumi Kokubo, Kenichi Kakimoto, Hitoshi Ohsato
Abstract: KNbO3 (KN) powder was synthesized by modified Pechini method (polymeric precursor method). KN powder with different crystal structure and grain size distribution was synthesized by different drying temperature. In this paper, the mechanism of preparation of KN powder was discussed in thermal decomposition behavior. The obtained powder was characterized by XRD, TEM, FT-IR and TG-DTA.
Authors: Xin Yan Wu, Wei Xiong
Abstract: Electronic structure and chemical bonding in tetragonal KNbO3 have been studied by first-principles calculations. The band gap is indirect and a value of 1.64 eV was determined. Chemical bonding feature shows that a significant hybridization between Nb 4d and O 2p states. The bonding between K and NbO3 is mainly ionic nature while covalent nature was confirmed between Nb and O.
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