The effects of alkaline earth metal ions and halogen ions on the chromium oxide activities in alkaline earth metal oxide-halide-Cr2O3 system fluxes

The solid electrolyte cell -Mo/Cr + Cr(2)O(3)parallel to Zro(2)(MgO)paralle l to{Cu-Cr}(alloy) + (Cr2O3)(fluxes)\Mo+ is used at 1673 K to determine Cr2 O3 activities in MO-MX2-Cr2O3 (M = Ca2+ Ba2+; X = F- or Cl-) ternary fluxes , which are in equilibrium with the copper-chromium binary alloy. The terna ry isothermal phase diagrams of CaO-CaF2-Cr2O3 and BaO-BaCl2-Cr2O3 system f luxes are inferred on the basis of the experimental results and binary phas e diagrams. The results indicate that Cr2O3 activities in all fluxes always decrease with the increase of the X-MO/X-MX2 ratio. Partial replacement of BaO in BaO-BaF2-Cr2O3 fluxes by CaO is acceptable for economy and efficien cy considerations. At the same time, partial substitution of BaO for CaO in CaO-CaF2-Cr2O3 fluxes is advantageous for phosphorus removal and chromium retention as a result of the increased Cr2O3 activities, increased basiciti es, and widening of the liquid zones. Compared to those in BaO-BaF2-Cr2O3 f luxes, Cr2O3 activities in CaO-CaF2-Cr2O3 fluxes approximately follow the s ame curve as the former, although the position and the width of the liquid zones are considerably different, and activities in BaO-BaCl2-Cr2O3 fluxes are higher at the lower Cr2O3 content, or vice versa. The activity coeffici ents of Cr2O3 in the fluxes decrease with the increase of the X-MO/X-MX2 ra tios.