Kinetics of Synthesis of Ba1.0Co0.7Fe0.2Nb0.1O3–δ through Solid-Solid Reaction

Abstract

The mechanism of solid-solid reaction between BaCO₃ and Co₃O₄/Fe₂O₃/Nb₂O₅ has been investigated by means of non-isothermal thermogravimetry and differential scanning calorimetry (DSC) under flowing air gas conditions at atmospheric pressure with a new solid-solid reaction model. The effects of high speed agitating mixing and ball-milling mixing processes on the synthesis kinetics were also studied. The synthesis kinetics of Ba_1.0Co_0.7Fe_0.2Nb_0.1O_3–δ from the BaCO₃ and Co₃O₄/Fe₂O₃/Nb₂O₅ particles was calculated by applying the modified model. The results indicated that the overall reaction process was considered involving two stages: addition reaction between BaCO₃ and Co₃O₄/Fe₂O₃/Nb₂O₅ particles in the first stage and solution reaction between BaCoO₃, BaFeO₃, and BaNbO₃ to form a homogeneous Ba_1.0Co_0.7Fe_0.2Nb_0.1O_3–δ phase in the second stage. The new model matched well with the experimental data. The apparent activation energy of addition reaction stage of the high speed agitating mixing sample was estimated to be 376.76 kJ·mol⁻¹, which was only 3/4 of that of the ball-milling mixing sample (494.76 kJ·mol⁻¹). These results indicated that the high-speed agitating process could enhance atomic diffusion and facilitate the subsequent reaction, thus it is believed as a more effective, energy saving, and environmentally benign mixing process.