Phase relations in the Nd-Ba-Cu-O system in reduced oxygen atmospheres

We have studied the quasi-binary phase diagrams along the line connecting NdBa2Cu3Oy and BaCuO2+w in reduced oxygen atmospheres: p(O2) = 10-3 and 10-2 atm. The nucleation and melt of NdBa2Cu3Oy (Nd123) in Ba-rich solvent were observed in situ using a laser scanning microscope in 1% O2 + Ar and 0.1% O2 + Ar. The liquidus and solidus lines of nearly stoichiometric Nd123 have been constructed. We have found that phase relations are quite different between 1% O2 + Ar and 0.1% O2 + Ar. In a 0.1% O2 + Ar environment BaCuO2+w undergoes incongruent melting (BaCuO2+w→Ba2CuO3+z + L→BaO + L) and Nd422 decomposes into the Nd2O3 phase.