Synthesis of new copper oxide superconductors at high oxygen pressure
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The stability of the copper ion in +1, +2, and +3 oxidation states for oxides synthesized at oxygen activity, 10−6<f(O2)<103 bar, makes possible formation of a wide variety of distinct structures since the copper ion in a particular oxidation state prefers a unique coordination to oxygen. Thus, by controlling the oxygen pressure during the synthesis and annealing, the distribution of metaland oxygen-ions can be modified on atomic scale to optimize the structural and electronic properties. We present several examples of compounds of which the critical structural elements for superconductivity, i.e. the perfectly ordered CuO2-planes, have been obtained and doped with holes by means of high oxygen pressure. These materials, La2CuO4+δ, La2-xCaxCuO4, La2-yCu2O6+° and GaSr2Y1-xCaxCu2O7, offer a unique opportunity to study the relationship between superconductivity and structural, magnetic, and chemical properties.
Key wordsHigh oxygen pressure synthesis La2CuO4+°, new Cu-oxide superconductors
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