Papers by Author: Wataru Sakamoto

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Authors: Masato Fujioka, Toshiaki Yamaguchi, Wataru Sakamoto, Koichi Kikuta, Shin Ichi Hirano
Abstract: The effect of poly ammonium acrylate (PAA-NH4) dispersant on the dispersibility of Pb(Zr,Ti)O3 (PZT) slurries and the piezoelectric properties of resultant PZT sintered bodies was investigated for the establishment of environmentally friendly aqueous processing. The dispersion state and viscosity of PAA-NH4-added PZT aqueous slurries strongly depended on the slurry pH. Well-dispersed PZT slurries with negligibly small Pb2+ dissolution were obtained in the alkaline side due to the electrostatic steric hindrance effect of adsorbed polyelectrolyte dispersant molecules with a high dissociation ratio of carboxylic acid groups. The homogeneous dense microstructure and the enhancement of the piezoelectric properties of PZT ceramic bodies were achieved by preparing the aqueous PZT slurry with an optimum amount of dispersant.
Authors: Yuya Ito, Makoto Moriya, Wataru Sakamoto, Toshinobu Yogo
Abstract: Ferroelectric 0.7BiFeO3-0.3BaTiO3 and 0.7BiFe0.95Mn0.05O3-0.3BaTiO3 thin films were prepared by the chemical solution deposition. Perovskite single-phase thin films with homogeneous surface morphology were successfully fabricated at 700°C on Pt/TiOx/SiO2/Si substrates. Although typical polarization (P)-electric field (E) hysteresis loops were observed for 0.7BiFeO3-0.3BaTiO3 thin films, their insulation resistance was relatively low at room temperature. Mn doping for Fe site of the 0.7BiFeO3-0.3BaTiO3 was very effective in improving leakage current properties. In 0.7BiFe0.95Mn0.05O3-0.3BaTiO3 thin films, the abrupt increase in leakage current was suppressed even at high electric fields, leading to the well-shaped P-E hysteresis loops at ambient temperatures. Remanent polarization and coercive field of the 0.7Bi (Fe0.95Mn0.05)O3-0.3Bi0.5Na0.5TiO3 films at room temperature were approximately 26 μC/cm2 and 130 kV/cm, respectively.
Authors: Shin Ichi Hirano, Toshinobu Yogo, Wataru Sakamoto, Akihumi Tosa
Authors: Narimichi Makino, Bong Yeon Lee, Makoto Moriya, Wataru Sakamoto, Takashi Iijima, Toshinobu Yogo
Abstract: Lead-free ferroelectric (Bi0.5Na0.5)TiO3 (BNT) thin films were prepared by chemical solution deposition. BNT and Mn-doped BNT precursor thin films crystallized in the perovskite single phase at 700 °C on Pt/TiOx/SiO2/Si substrates. The leakage current density of the perovskite BNT films, especially in the high applied field region, was reduced by doping with a small amount of Mn. Also, Mn doping markedly improved the ferroelectric properties of the films. 0.5 and 1.0 mol% Mn-doped BNT thin films exhibited well-shaped ferroelectric polarization (P) electric field (E) hysteresis loops at room temperature. Furthermore, the 1 mol% Mn-doped BNT films showed a typical field-induced strain loop, and the effective d33 values were estimated to be about 60 pm/V.
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