Abstract
With an attempt to increase the Cu valence, we synthesized the (La1−x Sr x )8Cu8O20−δ (8-8-20 phase) compounds with large x using an O2-HIP apparatus. By heat treatment in a high-pressure of oxygen gas (40 MPa), the 8-8-20 compounds were stabilized in the range of 0.25 ≤ x ≤ 0.65. Their crystal structures, characterized by x-ray Rietveld refinement and electron diffraction, are tetragonal, space group P4/mbm. The formal copper valence was found to increase with Sr concentration from 2.24 at x = 0.25 to 2.63 at x = 0.65, keeping the oxygen content constant around 20.0. Electrical resistivity and magnetic susceptibility showed only metallic behavior from room temperature down to 5 K with no sign of superconductivity.
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Kandyel, E., Adachi, S., Wu, XJ. et al. High Pressure Synthesis of (La1−xSrx)8O20, (0.25 ≤ x ≤ 0.65) with a Wide Solubility Range and High Cu-Valence. Journal of Superconductivity 13, 503–511 (2000). https://doi.org/10.1023/A:1007731915362
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DOI: https://doi.org/10.1023/A:1007731915362