Preparation of indium oxide powders by microwave plasma dehydration of indium hydroxide powders

• In2O3 was prepared from dehydration of indium hydroxide using microwave plasma.
• The result was compared with those of the electrical furnace and the thermal plasma.
• In2O3 prepared by the microwave plasma had the smooth surface.
• The smooth surface was derived by the enhanced diffusion in the microwave plasma.
• The enhanced diffusion led to the formation of the smooth surface.

Indium oxide was prepared from the dehydration of indium hydroxide using atmospheric-pressure microwave air plasma. Compared with the conventional thermal plasma processing that was performed with the vapor phase reaction, the solid-state reaction was attempted in this study because microwave plasma has an intermediate temperature that is comparable to the melting temperature of inorganic materials and between those of the electric furnace and the thermal plasma. The results were compared with those with the electric furnace and the thermal plasma. With both the microwave plasma and the electric furnace, the macro-morphologies of the raw material were maintained, which indicates successful dehydration. However, the micro-morphologies differed. The product of the microwave plasma had a smooth surface, whereas the product of the electric furnace had a cracked and rough surface. The cracks were regarded as the results of the poor diffusion of the dissociated water. In the microwave plasma, the high temperature and the fast heating rate enhanced the diffusion and controlled the formation of cracks. With the application of the thermal plasma, the nanoparticles were prepared due to the vaporization of the dehydrated material. Thus, the microwave plasma is considered applicable to the solid-state reaction accompanying degassing, without a change in the microstructure of the raw material.

Indium oxide particles were prepared by the dehydration of indium hydroxide using microwave plasma (MWP) and compared with those by electrical furnace (EF) and thermal plasma (TP). In case of applying MWP and EF, dehydration by solid state reaction was successfully performed but surface morphologies were different. Product of MWP had smooth surface whereas products of EF had rough and cracked surface. In case of applying TP, raw material was vaporized and then nanoparticles were prepared by vapor phase reaction.Figure optionsDownload as PowerPoint slide