SOLID STATE PHASE CHEMISTRY IN THE SUPERCONDUCTING SYSTEMS: Y-Ba-Cu-O AND La-Sr-Cu-O.

Sub-solidus phase relationships in the superconducting oxide systems of Y-Ba-Cu (950 degree C) and La-Sr-Cu (980 degree C) have been determined and are discussed in terms of the superconducting compounds which exist as stable phases at these synthesis temperatures. The compositional range of the Y//xBa//4// minus //xCu//2O//y '132' solid solution has been more precisely determined and lattice constants are reported. Phase relationships in the La-Sr-Cu-O system are presented for the first time. In addition to the K//2NiF//4 and Sr//3Ti//2O//7 structure solid solutions and the '415' compound already reported, a new solid solution of composition La//xSr//2// minus //xCu//3O//y (0 less than equivalent to x less than equivalent to 1) was discovered. Of the compounds in the Y-Ba-Cu-O and La-Sr-Cu-O systems, only the '123' and K//2NiF//4 structure phases are superconducting under any conditions employed to date.