Synthesis of In-In₂O₃ microstructures by close-spaced vapor transport (CSVT) and their transformation to In₂O₃ nanobelts at low temperature

Indium oxide (In₂O₃) microstructures were synthesized through carbothermal reaction by the close-spaced vapor transport (CSVT) technique at low temperatures and without the use of catalysts. Morphological characterization by scanning electron microscopy (SEM) showed that the CSVT technique provides high-efficiency for the mass transport at low temperatures, as low as 650 °C, considering that in the synthesis indium oxide powders were used as a source. In addition, it is observed that the microstructures are formed mainly of microcubes with microspheres attached on their faces. Measurements of X-ray (XRD), Raman, and Energy-dispersive X-ray spectroscopy (EDS) showed that the microcubes tend to the stoichiometry of In ₂O₃ and the microspheres have an excess of indium. Based on the above results, the microstructures were converted to In₂O ₃ nanobelts by a simple post thermal annealing for 16 h in a nitrogen environment, according to additional morphological and structural characterizations. The results revealed that the In₂O₃ nanobelts have several micrometers in length with rectangular cross sections in the range from 50 to 250 nm and correspond to body-centered cubic (bcc) In ₂O₃ single crystal. The growth mechanisms of the microstructures and nanobelts are discussed in detail. Finally, Photoluminescence spectrum showed a broad emission around 600 nm. Refined studies showed three peaks at 420, 592, and 673 nm, which were attributed to oxygen vacancies.