Characterization of T*-Phase Superconductors

Mixed rare earth oxides of the form La sub 2-x-y RE sub x M sub y CuO sub 4, where RE is a light rare earth and M is an alkaline earth, crystallize in the T*-structure which is intermediate between the T-structure of La sub 2 CuO sub 4 and the T'- structure of RE sub 2 CuO sub 4. With high pressure oxygenation these compounds become superconductive for x = 0.9 and y = 0.2, with transition temperatures T sub c - 35K. We report studies of the phase stability, transport, magnetic and crystallographic properties of these T*-phase superconductors and compare our results to those found in T- and T' type superconductors.