Takeyo Tsukamoto

Preparation of Various Oxide Films by an Electrophoretic Deposition Method: A Study of the Mechanism.

The electrification mechanism of an oxide particle in a bath was analyzed. The zeta-potentials of various oxide particles in an acetone bath were found to be positive. The data suggested that H+ ions are generated in an acetone bath containing a small amount of added I2 and H2O by the keto-enol equilibrium reaction and then adsorbed on the oxide resulting in positively charged particles. The adsorption of H+ ions was assumed to be of the type of mono-molecular adsorption. Moreover, the electrodeposition flocculation mechanism for the particle was also investigated. On the basis of a relation of electrophoretic current with depositing time well described by the Cottrell equation, it was suggested that the electrochemical reaction proceeds on the cathode substrate surface and that the rate-determining step arises from the diffusion of H+ ions in the deposited film.

How to make superconducting-anisotropy least in high-Tc cuprate superconductors

Abstract The guiding principles to reduce superconducting-anisotropy were derived for high-T c cuprate superconductors. Based on the principles, we have attained the least superconducting-anisotropy γ=1.6 for a Cu-based CuBa 2 Ca 3 Cu 4 O 12−y (Cu-1234) superconductor. Further lower superconducting-anisotropy has been proposed for Cu-1245 (γ=1.3) and Cu-1256 (γ≌1.0) Cu-based superconductors.

Fabrication of Ferroelectric BaTiO3 Films by Electrophoretic Deposition

BaTiO3 thick films on Pt substrates were fabricated by the electrophoretic deposition method. The suspension was prepared with fine powder (0.1 µm in diameter) of BaTiO3, acetone and iodine. Dense and strong films were formed in an applied DC field of 500 V/cm. The films sintered at 1200°C were crystallized into the tetragonal phase at room temperature. The coercive field Ec and the remanent polarization Pr were estimated to be 1.6 kV/cm and 2.1 µC/cm2, respectively, from the P-E hysteresis loop observation.

Saturation of THz-radiation power from femtosecond-laser-irradiated InAs in a high magnetic field

THz-radiation power from femtosecond-pulse-irradiated InAs is found to be saturated at the magnetic field around 3 T. Additionally, we find that this saturation magnetic field strongly depends on geometrical layout. Interesting magnetic-field dependence of the center frequency for THz radiation is also observed.

Preparation of Ferroelectric Bi4Ti3O12 Thin Films with c-Axis Orientation by Atmospheric-Pressure Metal-Organic Chemical Vapor Deposition

Ferroelectric Bi4Ti3O12 thin films were prepared by the metal-organic chemical vapor deposition (MOCVD) method at atmospheric pressure using Bi( o-C7H7)3 and Ti( i-OC3H7)2(DPM)2 as metalorganic sources. Assist Ar gas flow rate effects on the growth of the thin films were also examined. Thin films obtained were characterized by XRD analysis, SEM, AFM and D-E hysteresis loop observations. Most of the single-phase Bi4Ti3O12 thin films with c-axis orientation were deposited on Pt/Ti/SiO2/Si and Pt substrates above 500° C. Completely c-axis-oriented Bi4Ti3O12 thin films were prepared on Pt plates at 600° C, which showed good ferroelectric properties: remanent polarization of 1.0 µ C/cm2, coercive field of 18 kV/cm and leakage current on the order of 10-9 A/cm2.

Fabrication of Ferroelectric Bi4Ti3O12 Thin Films by Dipping Pyrolysis of Metal Naphthenates and Micropatterns by an Electron Beam

Fabrication of ferroelectric Bi4Ti3O12 thin films was carried out by dipping pyrolysis of metal naphthenates. Single-phase Bi4Ti3O12 thin films with c-axis orientation perpendicular to the substrate surface were fabricated on Pt plates. They exhibited good ferroelectric properties: coercive field of 7.7 kV/cm and remanent polarization of 8.2 µ C/cm2. For the films fabricated on Pt/Ti/ SiO2/Si substrates, however, the Bi2Ti2O7 phase mainly grew because of Ti diffusion into the bismuth titanate layer during the heat treatment. Fine micropatterns with linewidth of less than 1 µ m in precursors of Bi4Ti3O12 were formed by spin-coating, irradiation with an electron beam and development. They were crystallized into the Bi4Ti3O12 phase by successive pyrolysis and annealing. The reaction between the metal naphthenate films and energized electrons was studied by IR spectroscopic analysis.

Effects of O2 Gas Pressure in Heat Treatment on Surface Morphology and Electric Properties of Ferroelectric Bi4Ti3O12 Thin Films with c-Axis Orientation

Fabrication of ferroelectric Bi 4 Ti 3 O 12 thin films was carried out by spin-coating pyrolysis of Bi and Ti naphthenates and successive heat treatment in O 2 gas at various pressures. Heat treatment in O 2 gas at high pressure was effective for the fabrication of c-axis oriented Bi 4 Ti 3 O 12 thin films with a smooth surface and improvement of their electric properties. The thin film heat-treated at the O 2 gas pressure of 4.0 x 10 5 Pa was a single phase of Bi 4 Ti 3 O 12 completely oriented along the c-axis with good ferroelectric properties at room temperature : coercive field of 23 kV/cm, remanent polarization of 1.9 μC/cm 2 , dielectric constant of 45, loss of 0.01 and leakage current density on the order of 10 -9 A/cm 2 . The remanent polarization of the thin film was kept constant up to the polarization reversal at 1 x 10 7 cycles.

Protonic Conduction in the Single Crystals of SrZr0.95M0.05O3 (M=Y,Sc,Yb,Er).

The protonic conductivities of SrZr0.95M0.05O3 doped with four acceptor ions (M3+=Y3+, Sc3+, Yb3+, Er3+) have been studied in the single crystal form. The protonic conductivity is found in four acceptor ions, indicating that protons migrate by hopping from site to site. The Yb-doped crystal has the lowest activation energy and the highest conductivity amongst the four acceptor ions. This is considered to be due to the difference in strength of the O–H bond with different acceptor doping.

Sustained release of 17β-estradiol from poly (lactide-co-glycolide) microspheres in vitro and in vivo

Poly (lactide-co-glycolide) microspheres containing four different concentrations (0.15, 0.3, 1.5, 2.25% (w/w)) of 17β-estradiol, all of which are monolithic devices, were prepared by a solvent evaporation method. In the preparation process, poly (lactide-co-glycolide) was dissolved in dichloromethane and estradiol was then dissolved or partly dispersed in the solution. The polymer solution containing drugs was emulsified in water to prepare o/w emulsion. Effects of surfactants and aqueous polymers added to the outer aqueous phase upon the emulsion stability were studied. It was found that polyvinylalcohol effectively stabilizes the dichloromethane in water emulsion. Effects of the estradiol concentration in the microspheres upon its release rate were studied. When the estradiol concentration in the microsphere is less than 0.3% (w/w), estradiol molecules can be dissolved in polymer matrices. When the estradiol concentrations in the microspheres are 1.5 and 2.25% (w/w), however, estradiol crystals exist in a microsphere as a dispersion in the polymer matrices together with estradiol molecules dissolved in the matrices. Sustained release of estradiol from poly (lactide-co-glycolide) microspheres containing 0.15 and 0.3% (w/w) was observed for 30 days in both systems, while that from poly (lactide-co-glycolide) microspheres containing 1.5 and 2.25% (w/w) was observed for 100 days in both systems. It was found that the release of estradiol from poly (lactide-co-glycolide) microspheres is affected by the following three mechanisms: (i) the release of estradiol molecules accompanied with the removal of degraded short polymer chains; (ii) the dissolution of estradiol crystals into polymer matrices and aqueous solution and (iii) pore formation in polymer matrices caused by the polymer degradation. In vivo study, estradiol was released with a constant rate from poly (lactide-co-glycolide) microspheres containing 0.3% estradiol and the plasma concentration of estradiol was kept constant at 1.5 ng ml−1 for 50 days.

Cu1−xTlxBa2Ca3Cu4O12−y (Cu1−xTlx-1234) superconductor with Tc=126 K

Abstract The samples of Cu 1−x Tl x Ba 2 Ca 3 Cu 4 O 12−y (x=0∼0.5) system with low Tl concentration were prepared by a high pressure techniques. The Cu 1−x Tl x Ba 2 Ca 3 Cu 4 O 12−y (Cu 1−x Tl x -1234: x=0.4∼0.5) samples show Tc of 126 K and superconducting anisotropy of γ=4. Their Tc values are higher than those of parent materials of CuBa 2 Ca 3 Cu 4 O 12−y (Cu-1234) and TlBa 2 Ca 3 Cu 4 O 11 (Tl-1234) by 8 K and 4 K, respectively. The anisotropy of Cu 1−x Tl x -1234 system is close to the value (γ=3.5) of Tl-1234 and higher than that of Cu-1234 (γ=1.6.