The preparation of bulk and thick films of YBa/sub 2/Cu/sub 3/O/sub 7-y/ using a solution technique

The authors synthesized the high T/sub c/ superconducting oxide Yba/sub 2/Cu/sub 3/O/sub 7-y/ using a solution technique and compare the resultant properties to materials synthesized by solid state reactions. Because the cations are mixed at the microscopic level, they observe that this solution technique allows lower reaction temperatures and shorter reaction times to obtain the superconducting material. They yield materials with particle sizes of about 1 μm and having a narrow size dispersion (as compared to the typically 50 μm particle sizes obtained by solid state reactions). The smaller, uniform particle sizes yield denser compacts upon sintering. Densities of 90% have been achieved and metallic-like behavior improves and is correlated with increasing density. The solution derived materials superconduct at 91 K and have narrow transition temperatures (0.6K width) which the authors attribute to sample compositional and structural homogeneity. Because they are able to produce stable, viscous gels, the authors investigated the preparation of large area thick films on various substrates of technological interest (e.g. alumina, zirconia, strontium titanate)