Thermal-induced phase transition and assembly of hexagonal metastable In2O3 nanocrystals: A new approach to In2O3 functional materials

This paper reports on the thermal-induced performance of hexagonal metastable In2O3 nanocrystals involving in phase transition and assembly, with particular emphasis on the assembly for the preparation of functional materials. For In2O3 nanocrystals, the metastable phase was found to be thermally unstable and transform to cubic phase when temperature was higher than 600 °C, accompanied by assembly as well as evolution of optical properties, but the two polymorphs coexisted at the temperature ranging from 600 to 900 °C, during which the content of product phase and crystal size gradually increased upon increasing temperature. The assembly of In2O3 nanocrystals can be developed to fabricate In2O3 functional materials, such as various ceramic materials, or even desired nano- or micro-structures, by using metastable In2O3 nanocrystals as precursors or building blocks. The electrical resistivity of In2O3 conductive film fabricated by a hot-pressing route was as low as 3.72×10−3 Ω cm, close to that of In2O3 single crystal, which is important for In2O3 that is always used as conductive materials. The findings should be of importance for both the wide applications of In2O3 in optical and electronic devices and theoretical investigations on crystal structures.