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We have studied the quasi-binary phase diagrams of RE–Ba–Cu–O systems, in which rare earth (RE) site is composed of Nd, Sm and its mixture, along the line connecting RE123 and Ba 3 Cu 5 O y (035) in 1% O 2 and 21% O 2 in Ar. The nucleation and melting of REBa 2 Cu 3 O y and RE 2 BaCuO 5 /RE 4 Ba 2 Cu 2 O 10 were observed in situ and the liquidus lines were determined using a laser-scanning microscope. Phase identification was performed on the samples quenched from high temperatures through X-ray powder diffraction measurements and electron probe microanalysis.

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.

We have studied the quasi-binary phase diagram along the line of NdBa2Cu3Oy and BaCuO2 in 1%O2+Ar. In this study, the nucleation and melt of NdBa2Cu3Oy in Ba-rich solvent were observed in situ using a laser-scanning microscope under 1%O2+Ar. The liquidus and solidus lines of nearly stoichiometric Nd123 were constructed. Phase identification has been performed on the samples quenched from the reaction temperatures determined by differential thermal analyses through X-ray powder diffraction measurements and scanning electron microscopy.