Oxygen stoichiometry in Ba sub 2 YCu sub 3 O sub x, Ba sub 2 GdCu sub 3 O sub x and Ba sub 2 EuCu sub 3 O sub x superconductors as a function of temperature.

The oxygen stoichiometry of Y, Gd and Eu containing superconducting perovskites (of the form Ba sub 2 YCU sub 3 O sub x) was determined by measuring the oxygen evolution of these materials (in an initially evacuated closed system), as a function of temperature. Results show that both Eu and Gd containing superconductors undergo the orthorhombic/ tetragonal phase transition at a lower temperature than the Y analog, and that the Gd-sample tetragonal phase exhibits semiconductor behavior above 77K.