Solid-state equilibrium relations in the Ternary Systems TeO2?MoO3?MoO2 and TeO2?MoO3?Te

In a study of the solid-state reactions in the ternary systems TeO₂? MoO₃? MoO₂ and TeO₂? MoO₃? Te, approximately 70 selected compositions were sintered at 550°C to attain equilibrium conditions, and solid-state equilibrium relations were characterized by x-ray diffraction. In a large composition range, the interaction of TeO₂ and MoO₃ with the reducing agents MoO₂ or Te leads to the reduced ternary oxide TeMo₄O₁₃ (m. p. 748°C), in addition to Te₂MoO₇, Te and (intermediate) molybdenum oxides. The compatibility relations for the binary systems TeO₂? MoO₂ and MoO₃? Te are presented for the first time. In the TeO₂? MoO₂ system, three-phase regions are found: (Te₂MoO₇? TeO₂? Te) on the TeO₂? and (TeMo₄O₁₃? MoO₂? Te) on the MoO₂-rich sides with (TeMo₄O₁₃? Te₂MoO₇? Te) in the intermediate region. In the MoO₃? Te system, three-phase regions (TeMo₄O₁₃? MoO₂? Te), (TeMo₄O₁₃? Mo₄O₁₁? MoO₂) and (TeMo₄O₁₃? MoO₃? Mo₄O₁₁) were detected. TeMo₄O₁₃ presents two allotropic forms (α′ for T < 450°C, α for T > 450°C). Both structures have been characterized by I.R. and optical reflectance spectroscopy. Unit cell dimensions are also given.