Synthesis of Cubic In2O3 by a Liquid Plasma Method without Chemical Additives

Abstract

Cubic In(OH)(3) crystals were prepared by a liquid plasma method at 6 kV and 55 mA using an H-cell. The solution pH in the cathode increased with the reaction time up to 15 min due to proton reduction, which promoted the deprotonation of In aqua complexes. In(OH)(3) was formed by the deprotonation of these complexes during proton reduction. After 15 min, the pH in the cathode cell was significantly decreased, which was ascribed to proton transfer from the anode to the cathode. pH measurements showed that a pH difference between the cathode and anode cells developed during the reaction. Nucleation and crystal growth were monitored via high-resolution transmission electron microscopy and selected area electron diffraction analysis of samples prepared with different reaction times. Initially, small amorphous particles were formed by Ostwald ripening, and these particles rearranged to form rods with 50-90 nm lengths. Cubic In(OH)(3) crystals formed via the oriented attachment of the rods. Finally, cubic In2O3 crystals were prepared by calcining the In(OH)(3) samples. Photoluminescence emission peaks corresponding to green and orange emissions were observed for the In2O3 prepared by calcining the In(OH)(3) samples. Further, MPS analysis revealed oxygen defects in the In2O3 nanocubes.