FORMATION OF THEORETICAL-DENSITY MICROHOMOGENEOUS YBA2CU3O7-X USING A MICROEMULSION-MEDIATED PROCESS

We describe a new technique using microemulsions for synthesizing an ultra-homogeneous, microparticulate precursor for the production of sintered YBa2Cu3O7-χ. The process ensures a uniform mixing of the cations down to a scale of at least 10 nm. The finely dispersed oxalate precursor (particle size ≈ 50 nm) yields single-phase YBa2Cu3O7-χ powder (particle size ≈ 275 nm) on calcining at 820°C. The material sintered at 925°C has a very compact microstructure with large (15-50 μm) grains and has a bulk density that is about 98% of the theoretical (single-crystal) value. It also exhibits a significantly higher Meissner effect than the material produced by conventional aqueous precipitation when both are sintered under identical conditions. © 1990.