Preparation of superconducting YBa2Cu3O7-δ nanopowder by deoxydation in Ar before final oxygenation

Superconducting YBa2Cu3O7-delta nanopowder is prepared by the citrate-gel modification of the sol-gel method. Most important advantages of this method are the homogeneity at atomic level and possibility to reduce the calcination temperature to limit thermal agglomeration of the particles. A preparation temperature less than or equal to800 degreesC is used with a deoxydation step in Ar before the final oxidation. The X-ray diffraction data confirm the orthorhombic structure of the nanopowder. Superconducting properties are investigated with a SQUID magnetometer showing that the global T-c = 92 K. Single grains of the powder have average diameter of 60-80 nm, depending on the calcination process used. The grains are weakly connected stacks of flat particles having thickness of a few nanometer. (C) 2001 Elsevier Science B.V. All rights reserved.