Mechanism of Sm₂MoO₆ Phase Formation from a Mechanically Activated Oxide Mixture

The mechanism of phase formation from the initial and the mechanically activated (m/a) mixture of Sm₂O₃+MoO₃ oxides is studied by differential scanning calorimetry (DSC) in an oxygen atmosphere. It is shown that different mechanisms of samarium oxymolybdate synthesis are realized in these two cases. As a result of the mechanochemical action at room temperature, a nanosized mixture of Sm₂(MoO₄)₃ and Sm₂O₃ is formed. Upon heating, Sm₂(MoO₄)₃ is crystallized at the first stage and its interaction with Sm₂O₃ in the second stage at 900°C leads to the synthesis of oxymolybdate Sm₂MoO₆ with a scheelite structure, and this structure type is stable up to 1400°C. The kinetic experiment in a DSC cell shows only an apparent similarity of the phase formation mechanism with a decrease of the main exoeffects by 70°C for a m/a mixture of oxides. At the same time, the study of the mechanism of phase formation by isothermal exposure at different temperatures reveals the main advantages of ceramic synthesis from an activated oxide mixture. The total conductivity of Sm₂MoO₆ with a scheelite structure, which turned out to be of the p-type (1 × 10⁻⁶ S/cm at 600°C), is studied.