Crystal engineering of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// structures

In order to produce more stable and processable forms of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductors, a series of cation substitution reactions have been completed. Compounds in the family of Y/sub 1-y/Ca/sub y/Ba/sub 1-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// display an increased corrosion resistance with increasing substitution level. The composition of Y/sub 0.6/Ca/sub 0.4/Ba/sub 1.6/La/sub 0.4/Cu/sub 3/O/sub 6.96/-(T/sub c/=80 K) is found to be at least 100 times more stable than the parent compound, YBa/sub 2/Cu/sub 3/O/sub 6.94/. In this paper, compositions yielding transition temperature above 83-85 K have been identified in YBa/sub 2-x/Sr/sub x/Cu/sub 3/O/sub 7-/spl delta// and Gd/sub 1-x/Ca/sub x/Ba/sub 2-y/La/sub y/Cu/sub 3/O/sub 7-/spl delta// systems suggesting that the surface reactivity, processability and superconducting properties can be tailored with the use of the appropriate cation compositions. Rational approaches for the systematic tailoring of high-T/sub c/ superconductors based on lattice engineering approaches are thus developed.