Solid Phase Relations at 950°C in La‐Ba‐Cu‐O

Subsolidus phase relations in the La₂O₃–BaO–CuO system were studied at 950°C. Three previously reported binary compounds exist (La₂CuO₄, BaLa₂O₄, and BaCuO₂) and five previously reported ternary phases occur (La_2‐xBa_xCuO_4‐(x/2)+δ, La_4‐2xBa_2+2xCu_2‐xO_10‐2x, La_2‐xBa_1+xCu₂O_6‐(x‐2), La_3‐xBa_3+xCu₆O_14±δ, and La₄BaCu₅O_13+δ). Of the seven phases in the diagram, all but BaLa₂O₄, BaCuO₂, and La₄BaCu₅O_13+δ were shown to exhibit significant ranges of solubility. The diagram is important in that both >30 K (La_2‐xBa_xCuO_4‐(x/2)+δ) and >90 K (La_3‐xBa_3+xCu₆O_14+δ, x=1) superconductors occur.