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Featured researches published by Izumi Masuda.


Japanese Journal of Applied Physics | 2003

Ferroelectric and piezoelectric properties of KNbO3 ceramics containing small amounts of LaFeO3

Ken-ichi Kakimoto; Izumi Masuda; Hitoshi Ohsato

Dense KNbO3 ceramics have been successfully synthesized by pressure-less sintering under optimized heat-treatment conditions using a small amount of La2O3 and Fe2O3 additives. KNbO3 forms (K1-xLax)(Nb1-xFex)O3 solid solutions and changes in the crystal system, depending on the additive content, from orthorhombic to tetragonal at x of 0.020, and from tetragonal to cubic at x of 0.200 or higher. When only 0.002 mol of La2O3 and Fe2O3 (x=0.002) was added into KNbO3, the highest value (98.8%) of the theoretical density was obtained. This specimen showed orthorhombic symmetry with a high Curie temperature of 420°C, and demonstrated a well-saturated ferroelectric hysteresis loop with large remanent polarization (Pr) of 18 µC/cm2, which is comparable to the value reported for pure KNbO3 ceramics fabricated by hot pressing. Furthermore, the x=0.002 specimen showed a planar electromechanical coupling ratio (kp) of 0.17 and piezoelectric d33 constant of 98 pC/N, regardless of the unsaturated poling state.


Japanese Journal of Applied Physics | 2004

Solid-Solution Structure and Piezoelectric Property of KNbO3 Ceramics Doped with Small Amounts of Elements

Ken-ichi Kakimoto; Izumi Masuda; Hitoshi Ohsato

The origin of the improvement of the ferroelectric and piezoelectric properties of KNbO3 ceramics by the addition of small amounts of La and Fe has been investigated. The La/Fe-codoped KNbO3 ceramics formed a single (K1-xLax)(Nb1-xFex)O3 solid solution, and their unit-cell volume decreased significantly with an x of 0.002 mol, while they recovered at x=0.004. In this region, the lattice parameters of the a-b basal plane decreased and the elongation in the c direction toward apical oxygen in NbO6 octahedra occurred. These results were correlated with the enhanced polarization and piezoelectric properties measured for the x=0.002 specimen. The x=0.002 specimen demonstrated a kt of 0.48 which corresponds to approximately 70% of the kt value predicted for a KNbO3 single crystal as its maximized property. Furthermore, La/Fe-codoped KNbO3 ceramics with MnO2 addition were prepared to observe the effect of multivalent ion (Fe and Mn) doping into the KNbO3 structure on the properties. Synchrotron near-edge X-ray absorption spectroscopy (XANES) study revealed a mixture of k-edge spectra consisting of Mn4+/Mn3+/Mn2+, while Fe3+ maintained its valence state. The influence of valence fluctuation on the ferroelectric and piezoelectric properties of KNbO3 ceramics was discussed.


Japanese Journal of Applied Physics | 2002

Growth Morphology and Crystal Orientation of KNbO3 Film on SrTiO3 by Liquid Phase Epitaxy

Ken-ichi Kakimoto; Shinro Ito; Izumi Masuda; Hitoshi Ohsato

Single-crystalline KNbO3 (001) films were successfully formed on the SrTiO3 (001) substrate from high temperature K2CO3–Nb2O5 solution by liquid phase epitaxy (LPE) technique. The growth morphology was strongly influenced by the melt composition and film growth temperature. Translucency and defect formation were observed in the KNbO3 films grown from the melt with K2CO3 content of 52.5 mol% which is utilized for the bulk crystal growth. In contrast, a transparent single-phase epitaxial film was obtained by lowering the growth temperature from 1051 to 900°C using the melt with high K2CO3 content of 65.0 mol%. The crystallographic relationship between KNbO3 film and SrTiO3 substrate was also investigated by the precession X-ray photography.


Science and Technology of Advanced Materials | 2005

Development of transparent single-crystalline KNbO3 thin film by LPE technique

Ken-ichi Kakimoto; Tomohiko Hibino; Izumi Masuda; Hitoshi Ohsato

Abstract Single-crystalline KNbO3 thin film has been successfully formed on SrTiO3 substrate from high-temperature K2CO3–Nb2O5 solution by the liquid phase epitaxy (LPE) technique. The growth morphology was strongly influenced by the melt composition and film growth temperature. The starting material for the film preparation was a powder mixture of K2CO3 and Nb2O5. The oxides were mixed in non-stoichiometric proportion with excess K2CO3 as flux. Under the optimized film growth conditions using melt compositions including K2CO3/Nb2O5Z52.5/47.5, 60.0/40.0 and 65.0/35.0, transparent single-crystalline KNbO3 thin films could be obtained. The synthesized KNbO3 thin film was subjected to precession X-ray photography in order to evaluate the crystallographic relationship with SrTiO3 substrate, and the result was compared with a simulated diffraction pattern. The precession X-ray photography clearly indicated that the [010]KNbO3 is not placed on the same diffraction line as [010]SrTiO3 but is slightly shifted with a difference in angle of approximately 38, while the [100] and [001] agree in direction for KNbO3 and SrTiO3. The observed lattice parameter c of KNbO3 film was calculated to be4.043 Å which was slightly (1.7%) larger than 3.974 Å reported for KNbO3 bulk crystal. In-plane rotation and elongation toward substrate normal for KNbO3 lattice on SrTiO3 substrate were discussed from the viewpoint of release of elastic energy accumulated by lattice mismatch on the substrate.


Key Engineering Materials | 2004

Ferroelectricity and Solid-Solution Structure of KNbO3 Ceramics Doped with La and Fe

Ken-ichi Kakimoto; Izumi Masuda; Hitoshi Ohsato

Co-doping of La2O3 and Fe2O3, has to be found to work effectively as an additive for densification of KNbO3 ceramics through ordinary pressure-less sintering process. X-ray diffraction analysis revealed that the co-doped KNbO3 formed a single (K1-xLax)(Nb1-xFex)O3 solid solution and changed in the crystal system from orthorhombic to tetragonal at x of 0.020, and from tetragonal to cubic at x ≥ 0.200. X-ray absorption near edge structure (XANES) of Fe k-edge revealed that valence change of Fe might occur in the specimen with x=0.004. The x=0.002 specimen demonstrated a well-saturated P-E hysteresis loop with Pr of 18 μC/cm 2 and Ec of 9 kV/cm, and showed kp of 0.17, kt of 0.47 and d33 of 98 pC/N in the piezoelectric measurement.


Journal of The European Ceramic Society | 2005

Lead-free KNbO3 piezoceramics synthesized by pressure-less sintering

Ken-ichi Kakimoto; Izumi Masuda; Hitoshi Ohsato


Journal of Electroceramics | 2004

Ferroelectric Property and Crystal Structure of KNbO3 Based Ceramics

Izumi Masuda; Ken-ichi Kakimoto; Hitoshi Ohsato


Archive | 2004

Method of manufacturing potassium niobate sintered compact

Ken-ichi Kakimoto; Izumi Masuda; Hitoshi Osato; いづみ 増田; 齊 大里; 健一 柿本


Journal of Electroceramics | 2004

Single-crystalline KNbO3Thin film grown by liquid phase epitaxy

Ken-ichi Kakimoto; Izumi Masuda; Tomohiko Hibino; Hitoshi Ohsato


Journal of Electroceramics | 2004

Single-Crystalline KNbO 3 Thin Film Grown by Liquid Phase Epitaxy

Ken-ichi Kakimoto; Izumi Masuda; Tomohiko Hibino; Hitoshi Ohsato

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Ken-ichi Kakimoto

Nagoya Institute of Technology

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Hitoshi Ohsato

Nagoya Institute of Technology

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Tomohiko Hibino

Nagoya Institute of Technology

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Hitoshi Osato

Nagoya Institute of Technology

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Shinrou Ito

Nagoya Institute of Technology

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