Synthesis, $P-T$ phase diagram, and $T_c$ of $R_2Ba_4Cu_7O_{15}$ (R= Dy,Y, DyY, GdY )

ORAL

Abstract

The oxygen pressure - temperature phase diagrams of $R_2Ba_4Cu_{15}$ (R=Dy,Y, Er, DyY, GdY, and EuY) superconductors have been investigated in the temperature range between $850$ and $1025^{\circ}C$ and the pressure range between $1\,$ and $50\,atm.O_2$. The relative fraction of the phases: 123, 124, and 247, was determined by studying the intensity of the xray diffraction peaks of each phase. The condition at which the phase pure 247 exists was determined to be $P=10 \;atm$ and $T=1025^{\circ} C$. Under these conditions samples with larger size R = LaY, NdY, SmY, and Eu fail to form pure 247 phase. Annealing at $P=200 \; atm. O_2$ and $400 ^{\circ} C$ was used to increase oxygen content of the as-synthesized materials and to induce superconductivity. The highest transition temperatures of $70 K$ were observed for R=Y compositions.

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Authors

  • Seyed Ahmad Sabok-Sayr

    Department of Physics, Northern Illinois University

  • Bogdan Dabrowski

    Physics Department - Northern Illinois University and Materials Science Division - Argonne National Laboratory, IL USA, Department of Physics, Northern Illinois University, DeKalb, IL, Department of Physics, Northern Illinois University, Department of Physics, Northern Illinois University, DeKalb, IL and Materials Science Division, Argonne National Laboratory, Argonne, IL

  • Stanislaw Kolesnik

    Physics Department - Northern Illinois University, IL USA, Department of Physics, Northern Illinois University, DeKalb, IL, Department of Physics, Northern Illinois University, Department of Physics, Northern Illinois University, DeKalb, IL and Materials Science Division, Argonne National Laboratory, Argonne, IL, Northern Illinois University