Superconductivity of the single-phase compound ${\mathrm{Er}}_1$${\mathrm{Ba}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$: Transport and structural properties

We report electrical and structural measurements on the high-$T_c$ single-phase superconductor ${\mathrm{Er}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$. Our best samples have relatively low room-temperature resistance and superconducting onset temperature of 94 K. The structure of the single phase is found to be an orthorhombic perovskite similar to the one reported for the ${\mathrm{Y}}_1$ ${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$ compound, but different from the ${\mathrm{K}}_2$ ${\mathrm{NiF}}_4$ perovskite structure found in the earlier high-$T_c$ compounds. The calculated effect of possible oxygen deficiencies in several of the crystal planes will be discussed. The x-ray diffraction spectrum shows that there could be more than one phase present, depending on the preparation conditions.