Preferential Formation of High T c Phase in Nd-Ba-Cu-O Superconductors Melt-Processed in Reduced Oxygen Atmospheres

To identify a preferential formation of high T c phase (x<0.1) during melt processing in a reduced oxygen atmosphere among the Nd1+xBa2+xCu3Oy solid solutions, T c and the superconducting transition behavior for the samples fabricated using both various cooling rates and the isothermal growth at various high temperatures in a low oxygen partial pressure (PO2) were investigated. The relations between the processing conditions and the superconducting properties of the fabricated Nd-Ba-Cu-O samples supported that the formation of high T c phase was enabled by the suppression of Nd substitution for Ba sites in Nd1+xBa2+xCu3Oy solid solutions during the melt growth in a low PO2. Details could be qualitatively described by considering the melt processing conditions on the stability phase diagram of LOG [PO2(bar)] vs 1/T(K−1) showing different melting lines for various compositions x.