Masaki Suenaga

Substitutions for Cu in YBa2(Cu1−xMx)3O7−δ (M = Fe, Co, Al, Cr, Ni, and Zn)

Abstract Substitutions for copper in YBa 2 (Cu 1− x M x ) 3 O 7− δ (1:2:3) were investigated. It was found that indirect methods to determine solubility into 1:2:3 typically used in the study of intermetallic compounds (observed variation with composition of superconducting transition temperature and of lattice parameters) are not entirely reliable. Optical micrography was used to asses the morphology of the sintered polycrystalline specimens. Differential thermal analysis provides melting point data signaling the presence of impurities which melt at lower temperatures. Electron microprobe studies were undertaken to determine actual M content of the superconducting phase and to check for the presence of impurity phases. Estimates of solubility limits are made. Transmission electron microscope studies were used to determine the twin structure and investigate the occurrence of a tweed pattern. Superconducting transition temperature as a function of x was determined below the solubility limits. In several cases T c s observed in this work differ from some previous reports. Possible sources of these discrepancies are discussed. Variation of lattice parameters as a function of x is reported. Also described are electrical resistivity and DC susceptibility measurements for selected samples.

Effects of heat treatment and doping with Zr on the superconducting critical current densities of multifilamentary Nb3Sn wires

Various wire samples consisting of 19‐Nb3Sn filaments in a normal metal matrix were made by heat treating composite wires of 19‐Nb, Nb‐0.5 wt% Zr, Nb‐0.75 wt% Zr, and Nb‐2.5 wt% Zr filaments embedded in a Cu‐10 wt% Sn matrix. The Nb‐0.75 wt% Zr rod contained the precipitate ZrO2, while the Zr in the remaining Nb rods was in solid solution. The over‐all size of the composite was 2.5×10−2 cm and each filament was approximately 2.5×10−3 cm in diameter. The critical current density Jc at 4.2 °K was measured at 40 and 100 kG for a variety of heat treatments. It was found that the critical current density was a strong function of the thickness of the Nb3Sn layers formed during heat treatment. This dependence of Jc on the thickness d could be approximately represented by the expression Jc(d)≃J0 exp (−nd), where J0 is the extrapolated zero thickness critical current density. J0 was found to be approximately 2.4×106 A/cm2 at 40 kG for the Nb3Sn formed from pure Nb, 1.2×106 A/cm2 for Nb doped with solid‐solution ad...

Superconducting Properties of Multifilamentary Nb3Sn Made by a New Process

A new processing method for producing multifilamentary A‐15 superconducting composite wires in a ductile matrix is described. Nb3Sn made in this way was found to have a critical temperature of 17.5 K and a critical current density of 7.5×105 A/cm2 at 40 kG when suitably heat treated. The composite conductor could be bent with a radius of 2 cm or greater without appreciable degradation of its current‐carrying capacity.

Bi 2 Sr 2 CaCu 2 O 8 + δ Bicrystal c -Axis Twist Josephson Junctions: A New Phase-Sensitive Test of Order Parameter Symmetry

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Grain boundary diffusion and growth of intermetallic layers: Nb3Sn

{\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}

Growth rate limiting mechanisms of YBa2Cu3O7 films manufactured by ex situ processing

Josephson junctions between identical single crystal cleaves stacked and twisted an angle

SUPERCONDUCTING PROPERTIES OF MULTIFILAMENTARY V3Ga WIRES

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Kinetics of YBa2Cu3O7 film growth by postdeposition processing

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Critical‐current densities of bronze‐processed Nb3(Sn1−xGax) wires up to 23.5 T

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Grain-boundary studies by the coincident-site lattice model and electron-energy-loss spectroscopy of the oxygen K edge in YBa2Cu3O7-δ

axis. For each bicrystal, the ratio