Indium doped ZnO nano-powders prepared by RF thermal plasma treatment of In₂O₃ and ZnO

Indium doped ZnO nano-powders were synthesized by the RF thermal plasma treatment of In₂O₃ and ZnO. For this purpose, micron-sized ZnO powder was mixed with In₂O₃ powder at the In/Zn ratios of 0.0, 1.2, and 2.4 at. % by ball milling for 1 h, after which the mixtures were injected into RF thermal plasma generated at the plate power level of ∼140 kVA. As observed from the field emission scanning electron microscopy (FE-SEM) images of the RF plasma-treated powders, hexagonal prism-shaped nano-crystals were mainly obtained along with multi-pod type nano-particles, where the number of multi-pods decreased with increasing In/Zn ratios. In addition, the X-ray diffraction (XRD) data for the as-treated nanopowders showed the diffraction peaks for the In₂O₃ present in the precursor mixture to disappear, while the crystalline peaks for the single phase of ZnO structure shifted toward lower Bragg angles. In the UV-vis absorption spectra of the as-treated powders, redshifts were also observed with increases of the In/Zn ratios. Together with the FE-SEM images and the XRD data, the redshifts were indicative of the doping process of ZnO with indium, which took place during the RF thermal plasma treatment of In₂O₃ and ZnO.