Superconductivity in Sr0.75Y0.75Ba1.5Cu3 O7−d compounds
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- Siddiqi, S.A. & Anwar, M.S. Czech J Phys (2005) 55: 85. doi:10.1007/s10582-005-0010-5
The effect of simultaneous Sr substitution at the Ba and Y sites has been studied in the Sr0.75Y0.75Ba1.5Cu3O7−dsystem. Attempts to replace 25% Y and 25% Ba have been successful and superconductivity was observed above 78 K for Sr0.75Y0.75Ba1.5Cu3O7−d compound with ‘high oxygen content’, i.e., O6.76, and having orthorhombic crystal symmetry. The compound was treated in argon gas at 800°C to reduce the oxygen content and to induce some structural changes. The Sr0.75Y0.75Ba1.5Cu3O6.1 compound thus obtained has tetragonal symmetry and low oxygen content, O6.1. It has also shown superconductivity at 28 K. The paper presents a careful comparison of the structural and electrical properties and infrared absorbance spectra of the two compounds with the same metallic composition, Sr0.75Y0.75Ba1.5Cu3, but with different oxygen content and crystal symmetry. The study clearly establishes the occurrence of superconductivity in tetragonal Sr-substituted (both at Y and Ba sites in) “YBCO”.
Key wordssuperconductivity electrical resistivity infrared absorption spectroscopy YBCO
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