Synthesis of LaBa2Cu3O/sub 7-//sub y/ through tetragonal to orthorhombic phase transition at high oxygen deficiency

Superconductive LaBa2Cu3O/sub 7-//sub y/ materials which achieve zero resistivity at temperatures above 90 K have been synthesized using the appropriate sintering and annealing conditions. We find it necessary to sinter our samples in an inert atmosphere and to cool our samples from a high temperature to below the tetragonal to orthorhombic transition temperature in an inert atmosphere before the sample is further exposed to oxygen. We conclude that in order to produce amounts of orthorhombic LaBa2Cu3O/sub 7-//sub y/ material sufficient to achieve zero resistivity at temperatures of 90 K or above, it is necessary to prevent the material from incorporating too much oxygen while it is at temperatures in excess of its tetragonal to orthorhombic transition temperature