Construction of the Quasi‐ternary Phase Diagram in the NdO1.5‐BaO‐CuOx System in an Air Atmosphere: Part I, Equilibrium Tie Lines in the Nd1+xBa2−xCu3O6+δ Solid Solution and Liquid Region

Abstract

Quasi‐ternary phase diagrams of the NdO1.5‐BaO‐CuOx system near the CuOx corner have been constructed near the peritectic temperature in air of the Nd1+xBa2−xCu3O6+delta (Nd123) solid‐solution phase. Liquidus curves were determined by measuring the temperature dependences of the neodymium, barium, and copper solubilities in Nd‐Ba‐Cu‐O solutions with different BaO:CuO ratios. Solidus line compositions and equilibrium tie lines were determined by analyzing the compositions of the Nd123 solid solution equilibrated with the melt by quenching samples held isothermally. Based on the tie‐line features in the Nd123‐and‐ liquid two‐phase field, the Nd123 solid solution with the smaller substitution content was observed to be equilibrated with the solution melt with a higher BaO:CuO ratio, even in an air atmosphere. Nd123 crystal with a substitution content of ∼0.02 could be formed from the solution with the BaO:CuO ratio of greaterthan equal to0.75, which resulted in higher critical superconducting transition temperatures.