Liquidus Surfaces and Isothermal Section at 973 K of the BaO-ZnO-B₂O₃ Pseudo-Ternary System

Abstract

The liquidus surfaces and the isothermal section at 973 K of the pseudo-ternary BaO-ZnO-B₂O₃ system were determined using the thermal analysis and X-ray diffraction. The liquidus surface in equilibrium with ZnO spreads over a wide composition range and that in equilibrium with 5ZnO·2B₂O₃ extends long and narrow toward BaO·B₂O₃. The slope of the liquidus surface in equilibrium with ZnO is steep in the region of less than 20 mol%B₂O₃ but gentle when the B₂O₃ content exceeds 20 mol%. The liquidus surface in equilibrium with 3BaO·B₂O₃ widely extends and its slope is gentle in the region of less than 30 mol%B₂O₃ but steep when the B₂O₃ content exceeds 30 mol%. Pseudo-ternary BaO-ZnO-B₂O₃ compounds were not found in the composition range investigated. The ternary eutectic reactions are as follows: L→3BaO·B₂O₃+BaO·B₂O₃+ZnO, occurring at 1033 K at the composition 46.5 mol%BaO-14.5 mol%ZnO-39.0 mol%B₂O₃, L→BaO·B₂O₃+ZnO·B₂O₃+5ZnO·2B₂O₃, occurring at 1038 K at the composition 34 mol%BaO-21 mol%ZnO-45 mol%B₂O, L→BaO·2B₂O₃+BaO·4B₂O₃+ZnO·B₂O₃, occurring at 1008 K at the composition 19 mol%BaO-17 mol%ZnO-64 mol%B₂O₃.