Phase Equilibria of BaO-R2O3-CuO z Systems (R = Y and Lanthanides) under CO2-free Conditions

Abstract

For applications ranging from phase equilibria to the processing of second-generation high Tc superconductor-coated-conductors, phase diagrams constructed under carbonate-free conditions are needed. Subsolidus phase equilibria of BaO-R2O3-CuOz (R = Ho) have been investigated at \( {\hbox{p}}_{{{\rm{O}}_{{\rm{2}}} }} \hbox{\,=\,} 100\;{\hbox{Pa}} \) (810°C), 21 kPa (875°C) and 0.1 MPa (850 and 930°C) by applying controlled atmosphere methods to minimize the presence of carbonate and CO2 and H2O contamination. Under carbonate-free conditions, most of these phase diagrams are different from those reported in the literature. In this paper, we also review and compare the phase diagrams of ten BaO-R2O3-CuOz systems (R = Nd, Sm, Eu, Gd, Dy, Y, Ho, Er, Tm and Yb) that were previously determined in this laboratory under \( {\hbox{p}}_{{{\rm{O}}_{{\rm{2}}} }} \hbox{\,=\,} 100\;{\hbox{Pa}}{\hbox{.}} \) Among these diagrams, a distinct trend of phase formation and tie-line relationships is observed.