It is well known that, in the YBa2Cu3O7-x (Y-123) system, the orthorhombic phase is superconducting, due to the formation of ordered chains that act as dopants for the two-dimensional CuO2 planes, while in the tetragonal ordering these chains are absent, thus inhibiting the charge transfer from the CuO2 planes and making this phase insulating. Within this context, we have investigated the effect of chemical cationic substitutions such as Al, Sb, Te and Ca, of anionic doping (O2) and of X-ray nanobeam irradiation on both the electrical and the structural properties of high-Tc superconducting micro-crystals. These micro-crystals, multilayered structures characterized by a high spatial ordering, low defects concentration and excellent superconducting features, are ideal candidates for the study and the design of THz devices based on intrinsic Josephson Junctions. In this work, we present some structural and superconducting modifications induced on Y-123 micro-crystals by chemical co-doping with both Ca, Al and Te, to improve properties as aspect ratio (length/width), morphology, yield and Tc. In particular, we propose a superconducting and fully ordered tetragonal structure, with space group P4/mmm, which is obtained from the orthorhombic structure of YBa2Cu3O6.5 but with the chains running along the a axis as well as along the b axis. In this structure, previously invoked by Gupta et al., the Cu(1) atoms in the plane of the chains have twofold, square-planar fourfold, and sixfold coordinations, in contrast to the purely square-planar coordination in orthorhombic Y-123. This structure results from single crystal X-ray diffraction data and turns out to be superconducting from R vs T characterization.
Evidence of superconductivity in ordered tetragonal YBa2Cu3O7-x micro-crystals induced by chemical substitution
PASCALE, LISE;AGOSTINO, Angelo;TRUCCATO, Marco;OPERTI, Lorenza
2014-01-01
Abstract
It is well known that, in the YBa2Cu3O7-x (Y-123) system, the orthorhombic phase is superconducting, due to the formation of ordered chains that act as dopants for the two-dimensional CuO2 planes, while in the tetragonal ordering these chains are absent, thus inhibiting the charge transfer from the CuO2 planes and making this phase insulating. Within this context, we have investigated the effect of chemical cationic substitutions such as Al, Sb, Te and Ca, of anionic doping (O2) and of X-ray nanobeam irradiation on both the electrical and the structural properties of high-Tc superconducting micro-crystals. These micro-crystals, multilayered structures characterized by a high spatial ordering, low defects concentration and excellent superconducting features, are ideal candidates for the study and the design of THz devices based on intrinsic Josephson Junctions. In this work, we present some structural and superconducting modifications induced on Y-123 micro-crystals by chemical co-doping with both Ca, Al and Te, to improve properties as aspect ratio (length/width), morphology, yield and Tc. In particular, we propose a superconducting and fully ordered tetragonal structure, with space group P4/mmm, which is obtained from the orthorhombic structure of YBa2Cu3O6.5 but with the chains running along the a axis as well as along the b axis. In this structure, previously invoked by Gupta et al., the Cu(1) atoms in the plane of the chains have twofold, square-planar fourfold, and sixfold coordinations, in contrast to the purely square-planar coordination in orthorhombic Y-123. This structure results from single crystal X-ray diffraction data and turns out to be superconducting from R vs T characterization.
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