Papers by Author: Kiyotaka Tanaka

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Authors: Kazuyuki Suzuki, Kiyotaka Tanaka, Tatsuo Kimura, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
Abstract: The (Y,Yb)MnO3 films were crystallized on Y2O3 layers using alkoxy-derived precursor solutions. As a result of investigation of the effect of the Y2O3 layer on the dielectric properties of the (Y,Yb)MnO3/Y2O3/Si, the crystallographic properties such as the orientation and surface morphology of the (Y,Yb)MnO3 thin films depended on the crystallographic appearance of the insulator layer. Following that, the dielectric properties of the MFIS structures varied. For the construction of excellent MFIS structure, the improvement of the orientation, crystallinity, and surface smoothness of the (Y,Yb)MnO3 film by the optimization of the microstructure and dielectric property of the insulator is necessary.
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Authors: Kiyotaka Tanaka, Kazuyuki Suzuki, De Sheng Fu, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
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Authors: Kazuyuki Suzuki, Kiyotaka Tanaka, De Sheng Fu, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
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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.
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Authors: Kiyotaka Tanaka, Kazuyuki Suzuki, Tatsuo Kimura, Kaori Nishizawa, Takeshi Miki, Kazumi Kato
Abstract: Lead-free Ba(Ti1-xZrx)O3 (BTZ) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by the chemical solution deposition (CSD) process. The microstructure of the BTZ (x = 0.00 to 0.20) thin films was improved by additional sintering process, and their crystallite sizes were increased in each composition. The dielectric constant er and piezoelectric constant d33 of the BTZ thin films depended on the crystallite size. We give a guide for further investigation to improve the characteristics of BTZ thin films.
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Authors: Kaori Nishizawa, Takeshi Miki, Kazuyuki Suzuki, Kiyotaka Tanaka, Kazumi Kato
Abstract: The UV-Vis absorption spectrum of ZrO2 precursor solution containing 4-(phenylazo)benzoic acid (C6H5N=NC6H4COOH) reversibly changed accompanied with reversible change of the spectrum of 4-(phenylazo)benzoic acid by light irradiation. However, the spectrum of ZrO2 precursor solution containing azobenzene (C6H5N=NC6H5) did not change accompanied with reversible change of azobenzene by light irradiation. Furthermore, the back reaction of ZrO2 precursor solution containing 4-(phenylazo)benzoic acid by visible light irradiation was suppressed even if the back reaction of 4-(phenylazo)benzoic acid has occurred by visible light irradiation, when the hydrolysis of ZrO2 precursor was suitably controlled.
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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.
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Authors: Yutaka Yoshida, Yuji Ino, Kiyotaka Tanaka
Abstract: Based on a series of Mössbauer spectroscopic investigations on Fe impurities in p-type and n-type Si materials, we propose a new model for Fe impurities in Si matrix, consisting not only of interstitial Fe, but also substitutional Fe atoms with different charge states. Mössbauer spectroscopy enables us to observe directly these components which transform each other by changing external conditions such as under light illumination, under external voltage, and also under external stress. This means that not only interstitial Fe impurities, but also substitutional Fe impurities appear to be a source for producing “electrically active Fe impurities” in Si materials.
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