Chemical Problems Associated with the Preparation and Characterization of Superconducting Oxides Containing Copper

摘要

The superconducting oxides La(1.8)Sr(0.2)CuO4 and Ba2YCu3O7 were prepared by decomposition of mixed metal nitrates. Thermogravimetric analysis and electron spin resonance measurements indicated the presence of Cu(I) and Cu(III) in the La(1.8)Sr(0.2)CuO4 phase. The compound Ba2YCu3O7 prepared from the nitrates and subjected to an oxygen anneal at 425 C gave a sharp superconducting transition at 92 K. The phase was stoichiometric but readily decomposed when kept in contact with moist air.