Abstract
Surface carbonate ion observed in YBa2Cu3Ox from a conventional ceramic method was removed during vacuum calcination up to 1200 K. No surface condensation of Y and Ba due to the formation of the Y-CO3 and Ba-CO3 bond was observed in YBa2Cu3Ox prepared by vacuum calcination and subsequent oxidation in a pure oxygen atmosphere. YBa2Cu3Ox prepared by this process had a lower ΔTc value and low temperature coefficient of electrical resistivity than those observed in the sample from the conventional ceramic method. The existence of carbonate ion at the surface and grain boundaries had adverse effects on the superconducting properties of the products.
