Nobuhiko Kubota

Superconductivity in (Ca, Na)2CaCu2O4Cl2 The new simplest double-layer cuprate with apical chlorine

Abstract A new superconductor, (Ca,Na) 2 CaCu 2 O 4 Cl 2 ( T c = 49 K), with apical chlorines synthesized under high pressure has been found by resistivity and magnetization measurements. An X-ray powder diffraction study shows that the phase has a tetragonal structure with a = 3.85 A c = 21.45 A , and it has the so called La 2 CaCu 2 O 6 (2126) type structure with the apical site of pyramidal CuO 5 being occupied by the chlorine atoms.

Anisotropy of Bi-Sr-Ca-Cu-O Thin Film Growth

The growth mechanism of the superconducting Bi-Sr-Ca-Cu-O thin films were examined. The films were fabricated on Y3Al5O12(YAG) single crystal substrates by metalorganic chemical vapor deposition (MOCVD). The microstructure of the film was investigated by atomic force microscopy (AFM) and cross-sectional high-resolution transmission electron microscopy (HREM). The anisotropic growth were observed in this film. The modulated structure of Bi-Sr-Ca-Cu-0 thin films makes the main contribution to this anisotropic growth.

Preparation of Superconducting Thick Films of Bi-Sr-Ca-Cu-Oxide Using Plasma Spraying Method under Ambient Pressure

The system using plasma spraying of chemical solution in low power has been used to prepare superconducting Bi2Sr2Ca1Cu2Ox films under ambient pressure. Film as deposition on SrTiO3(100) gave Tc(onset) of 80.0K, Tc(R=0) of 72.6K. And the morphology of the film as deposition was that grain like crystal was grown. On two kinds of substrates was possible to prepare films which had good superconducting properties and morphology, in spite of high rate (1–2μm/hr) for deposition under ambient pressure.

Fabrication of Thick Films of YBa2Cu3Ox Superconductors Using Fine Particles Prepared by Mist Pyrolysis Method

Fine powders of Y-Ba-Cu oxide superconductor were prepared by mist pyrolysis process. Thick films were fabricated by deposition of the powders on MgO(100) substrate. Using Ag as a buffer layer could give the texture with c-axis of 123 phase perpendicular to the surface and sharp superconducting transition(Tc=80K, Jc=1.8×104A/cm2 at 65K) after sintering in Ar flow at 1323K followed by O2 annealing under 1073K.