Structural and optical characterization of crystals obtained via solid state reactions in the In₂O₃–TiO₂–Al₂O₃ pseudoternary system

In this article, a synthesis of the compound In₂O₃–TiO₂–Al₂O₃ (molar relation 3:4:1 and 5:8:1) at 1350 °C by solid-state reactions is described. The compounds were obtained after heat treatment at 1350 °C for two days. X-ray diffraction patterns indicate that the synthesized samples belong to the monoclinic crystal system with the space group C 2/m. An agglomeration of the crystals was observed by scanning electron microscopy for the heat-treated samples of either composition (S1HT and S2HT). Atomic quantitative analysis showed variations of the two compositions presented and TEM analyses confirmed that In₃Ti₂AlO₁₀ crystals were formed. Partial nanocrystallization and irregularities can be observed in the micrographs. Both samples were polymorphic and presented chain discontinuities attributed to oxygen vacancies and/or distortions in the structure. UV–vis measurements were performed obtaining a band gap ~ 3.2 eV for all the samples analyzed. XPS analysis for S1HT and S2HT confirmed the expected oxidation of the compounds.