THE OXALATE ROUTE TO SUPERCONDUCTING YBA2CU3O7-X

High-Tc superconductors can be easily obtained via the coprecipitation of nitrate and acetate aqueous solutions by oxalic acid. The thermal behavior of the amorphous precipitate is followed by X-ray diffraction. The superconducting YBa//2Cu//3O//7// minus //x orthorhombic phase is obtained upon heating at 860 degree C. Moreover, a pure tetragonal phase is already formed at temperatures as low as 720 degree C. This new phase appears to be somewhat different from the usual tetragonal phase. It does not transform into the orthorhombic phase when heated in oxygen between 400 degree C and 500 degree C.