| High-temperature superconductivity in yttrium barium copper oxide (YBa2Cu3O7) and related perovskite oxides: some aspects of solid state chemistry (1987) | |||||||||
Abstract | |||||||||
| Thermogravimetry and Cu "K-absorption edge measurements show that the superconducting $YBa_2Cu_30_7$ sample (annealed in $0_2$) contains more oxygen than the nonsupe conducting sample annealed in-$N_2$, the former has s less distorted structure with the actual composition not far from the ideal one. Oxides of the formula $Y_{l-x} Ba_2Cu_30_7$ (x = 0.05, 0.10 and 0.15) annealed in oxygen also possess the perovskite structure and show high-$T_c$ superconductivity. The superconduccting transition temperature seems to generally increase with the nominal $Cu^{3+}/Cu^{2+}$ ratio in the superconducting copper oxides. Control of the $Cu^{3+}/Cu^{2+}$ ratio (and hence the density of states at the metal-nonmetal transition in the non-superconducting state) through the oxygen stoichiometry or an appropriate cation substitution seems to provide a basis for synthesizing high-$T_c$ copper oxides. | |||||||||
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