The existence region of Eu(Ba1-x/2Eux/2)(2)Cu3Oz solid solutions at various oxygen pressures

Existence regions for Eu(Ba2-xEux)Cu3Oz solid solutions at various oxygen p ressures (p(O2) = 1 or 5.8 x 10(-4) atm) are studied. Fragments of quasi-bi nary joins BaCuO2-"Eu2BaCu3Oz" are mapped. It is established that the exten t of substitution of europium for barium is the highest in an oxygen flow a t T = 1000 degrees C (x(lim) = 0.7) and is reduced substantially as the oxy gen partial pressure decreases (x(lim) approximate to 0.3, p(O2) = 5.8 x 10 (-4) atm, 900 degrees C). It is found that the scenario of phase relations in the Eu(Ba2-xEux)Cu3Oz system at x > 0.7 is different from the phase beha vior of the NdO1.5-BaO-CuO and SmO1.5-BaO-CuO systems, which were studied p reviously. Specifically, the Eu(Ba2-xEux)Cu3Oz-Eu2BaCuO5-CuO equilibrium is observed in the sub-solidus region. In studying the influence of substitut ion and melt processing conditions on the superconducting properties of Eu1 +xBa2-xCu3Oz solid solutions, partial solid-state decomposition was observe d upon a low-temperature oxidizing anneal.