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.

*supported by the Institute for Nano Science, Engineering, and Technology (InSET) at NIU

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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