低温工学
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
最新号
選択された号の論文の10件中1~10を表示しています
巻頭言
特集:低温域における精密計測技術
解  説
テーマ解説
  • ―熱伝導率・熱拡散率,比熱容量,熱膨張率―
    阿子島 めぐみ, 山田 修史, 阿部 陽香
    2021 年 56 巻 1 号 p. 24-31
    発行日: 2021/01/20
    公開日: 2021/01/28
    ジャーナル フリー

    Thermophysical properties are widely used in thermal design for saving energy and safety and security. In order to secure reliability in these areas, the National Metrology Institute of Japan (NMIJ) has developed some precision measurement techniques. This paper describes details of the guarded hot-plate method for thermal conductivity, the flash method for thermal diffusivity, the adiabatic calorimetric method for specific heat capacity and the optical heterodyne interferometric method for thermal expansion coefficient. These methods give SI traceable thermophysical property values and well evaluated uncertainties.

研究論文
  • 森口 凱安, 土屋 雄司, 一野 佑亮, 吉田 隆
    2021 年 56 巻 1 号 p. 32-37
    発行日: 2021/01/20
    公開日: 2021/01/28
    ジャーナル フリー

    A high Q value for resonant circuits is necessary for wireless power transfer. The resistance in the circuit degrades the Q factor; thus, it is important to use elements with a low internal resistance such as superconductors. In this study, we focused on reducing the internal resistance in capacitors by using superconducting electrodes. We fabricated a multilayered structure with epitaxially grown BaTiO3 films on biaxially oriented YBa2Cu3Oy films and measured the superconducting and dielectric properties. As a result, the multilayered film showed superconducting transition at 86.1 K and a large reduction in ESR at temperatures below 90 K. The temperature dependence of the capacitance density peaks at 265 K and coincides with the structural phase transition of BaTiO3. The relative permittivity εr of the multilayered structure was 1.9-23.3, possibly due to a lower crystalline orientation.

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