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  • 1990-1994  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Emission life and surface analysis of barium-impregnated thermionic cathodes (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6482-6487 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Emission life of small Ba-impregnated thermionic cathodes suitable for use in TV tubes is investigated systematically. Cathodes are covered with an Os layer to enhance the emissivity. They have an unusual emission life in that the emission current decreases gradually with time and then drops abruptly. The early gradual decrease in emission at high cathode temperatures is caused by the phase change of the Os layer to OsW2. A linear relationship is found to exist between the logarithm of the lifetime and the reciprocal of the cathode temperature. This life end is believed to happen after the end of the reduction reaction between BaO and the porous W body and after ceasing replenishment of the low work function Ba+-O− monolayer on the metal surface. A formula for the emission lifetime is derived from the assumption that the rate determining step is the Ba diffusion inside the pellet. Emission lifetime τ is shown to be given by τ=Ad2 exp(E/kT), where A is a constant, d is the pellet thickness, and E is the activation energy of Ba diffusion. This relation is confirmed experimentally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355136
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical conductivity of a pure C60 single crystal (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2162-2163 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The temperature dependence of the electrical conductivity of a C60 single crystal is presented in this letter. The single-crystal samples free from solvent contamination were grown up to a size of millimeters order by sublimation of C60 powder with oscillation of the crystal temperature. The electrical conductivity of the single crystal was measured at temperatures between 250 and 295 K. The sharp decrease of the electrical conductivity with temperature around 256 K was observed in association with the phase transition of C60.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108281
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of high-T c Bi1.6Pb0.4Sr2Ca2(Cu0.9Ti0.1)3O x (1993)
    Springer
    Journal of materials science 28 (1993), S. 5262-5264 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Influences of sintering conditions onT c are studied for Bi1.6Pb0.4Sr2Ca2(Cu0.9Ti0.1)3O x . HighT c values are obtained at 1123±5 K sintering temperature and over 50 h sintering time. In order to explain theT c changes, morphological discussion is attempted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570075
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    Paper (German National Licenses)
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