The production of high performance YBa2Cu3O7 using nitrogen dioxide

Abstract

Energy Dispersive X-ray Spectroscopy (EDS) was used to show that the elemental homogeneity of YBa2Cu3O7 powders can be improved substantially by heating the powder in a nitrogen dioxide-containing atmosphere (e.g., 950°C), followed by annealing in oxygen at 950°C, and slow-cooling to room temperature. The improved homogeneity results in a substantially larger flux exclusion signal for the NO2-treated powder, as measured by both ac and dc techniques. The experimental results suggest a mechanism which involves the formation of a small amount of molten Ba(NO3)2, which acts as a flux that dissolves the constituents and reprecipitates them as high purity YBa2Cu3O7.