Browsing by Author "Sakata, Hironobu"

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    Electrical conductivity of V₂O₅-SnO-TeO₂ glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Mori, Hidetsugu; Igarashi, Jun; Sakata, Hironobu
    Electrical conductivity of glasses in the system V₂O₅-SnO-TeO₂ prepared by press quenching is measured and the mechanism of conduction related to glass composition is discussed. The glass forming region was found in the composition range (in mol%): 0 to 70 V₂O₅, 0 to 30 SnO and 30 to 100 TeO₂. Dc conductivities ranged from 2.1 * 10⁻⁵ to 5.4- 10⁻⁴ S/cm at 473 K for V₂O₅ concentrations of 20 to 60 mol%. The glass 20V₂O₅ * 20SnO * 60TeO₂ was more conductive (σ = 2.6 * 10⁻⁴ S/cm at 473 K) than the glasses V₂O₅ * 20SnO * (80 - X)TeO₂ with X=30 and 40 mol% (σ = -1.0 to 1.4 * 10⁻⁴ S/cm at 473 K). The electric conduction was attributed to adiabatic small-polaron hopping for V₂O₅ ≥ 50 mol% and non-adiabatic small-polaron hopping for V₂O₅ ≤ 50 mol%. The SnO content is contributed to increase basicity and decrease activation energy. The polaron bandwidth / ranged from 0.02 to 0.07 eV depending on the V-V ion spacing. The estimated carrier mobilities were remarkably small: 1.3 * 10⁻⁶ to 4.5 * 10⁻⁵ cm²/(Vs) at 473 K. This small mobility confirmed the small-polaron hopping conduction mechanism. The carrier density was evaluated to be 2.1 * 10¹⁹ to 2.1 * 10²¹/cm³ for V₂O₅ concentrations of 20 to 60mol%.
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    Optical properties of In2O3-coated cover glass for solar collectors
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1992) Noguchi, Satoshi; Mizuhashi, Mamoru; Sakata, Hironobu
    Visible and infrared optical properties of tin-doped In2O3 films were examined with regard to their electrical properties so as to be able to meet the requirements made on a solar collector operated at 100 °C. Reflectances and transmittances were calculated on the basis of the Drude theory as functions of the density and mobility of carrier and the film thickness. A good agreement between measured and theoretical reflectances indicates that this theory can describe the optical properties of the films. The calculations predicted a carrier density of about 3 · 10^20/cm^3 for the cut-off wavelength at 2 μm, the most effective minimum thickness of 400 nm, and the highest possible carrier mobility of e.g. 40 cm^2/(V s) to raise the selectivity for solar energy. Selective transparent films could be prepared by controlling the mobility and density of carrier with the introduction of about 1 wt% SnO2 or with annealing the films with 5 wt% SnO2 in air at 400 °C. From these results, it is concluded that the evaluation of the optical selectivity of In2O3 films can be achieved by determining their electrical properties.