CRYSTAL ENGINEERING OF YBA2CU3O7-DELTA STRUCTURES

In order to produce more stable and processable forms of YBa2Cu3O7-del ta superconductors, a series of cation substitution reactions have bee n completed. Compounds in the family of Y-1-yCayBa1-yLayCu3O7-delta di splay an increased corrosion resistance with increasing substitution l evel. The composition of Y0.6Ca0.4Ba1.6La0.4Cu3O6.96 (T-c = 80 K) is f ound to be at least 100 times more stable than the parent compound, YB a2Cu3O6.94. In this paper, compositions yielding transition temperatur e above 83-85 K have been identified in YBa2-xSrxCu3O7-delta and Gd1-x CaxBa2-yLayCu3O7-delta systems suggesting that the surface reactivity, processability and superconducting properties can be tailored with th e use of the appropriate cation compositions. Rational approaches for the systematic tailoring of high-T-c superconductors based on lattice engineering approaches are thus developed.