Investigation of the Ternary Reciprocal System Na,Ba||Br,MoO4

Abstract

Theoretical partition of the ternary reciprocal system Na,Ba||Br,MoO₄ into simplexes was performed, the stable diagonal of the system was determined, and the heat of the reaction at the conversion point was calculated. The chemical interaction in the system and the phase equilibria were described, and the crystallization fields of phases were delimited. The validity of the theoretical partition was confirmed by experimental investigation of the stable diagonal and two stable elements of the ternary reciprocal system Na,Ba||Br,MoO₄ by differential thermal analysis. It was found that the system Na,Ba||Br,MoO₄ is a singular irreversible reciprocal system with eutectic melting. The system is divided by the stable cutting diagonal NaBr–BaMoO₄ into two stable phase triangles, NaBr–BaBr₂–Na₂MoO₄ and NaBr–BaMoO₄–Na₂MoO₄. The results of the partition were corroborated by the X-ray powder diffraction analysis data. In the stable cutting diagonal, a saddle quasi-binary eutectic point, e 721°C, was revealed. The coordinates (melting point and composition) of two ternary eutectics, E₁ 586°C and E₂ 525°C, were found. The maximum crystallization field in the composition square corresponds to high-melting barium molybdate.