Synthesis, characterization, thermal stability and redox behavior of In3+2Ti4+1-xTm3+xO5-δ (Tm =Fe3+ and Cr3+, 0.0 ≤ x ≤ 0.2) mixed-oxide catalysts

Mixed metal oxide catalysts with nominal compositions of In2Ti1-xFexO5-delta In2Ti1-xCrxO5-delta where 0.0 <= x <= 0.2, have been synthesized by the ceramic route and characterized using the powder x-ray diffraction technique. The In2T1-xFexO5-delta samples were single-phase compositions, isomorphic with In2TiO5 phase. The particle size of the In2Ti1-xFexO5-delta samples was lower compared to the parent In2TiO5 oxide. Thermal stability (by thermogravimetry-differential thermal analysis) in varying atmospheres, and temperature-programmed reduction (TPR)/temperature-programmed oxidation cycles have been recorded to investigate their redox behavior as a function of the value of x in this study. The amount of H-2 consumed under TPR curves was correlated with the nonstoichiometry generated in the In2Ti1-xFexO5-delta samples. Fe substitution induced ease in the reducibility (i.e., maximum temperature) of the substituted oxides compared to that in In2TiO5. X-ray photoelectron spectroscopy has been used to confirm the oxidation states of indium and other metal ions in fresh and reduced samples.