Oxygen vacancies regulation of In₂O₃ for enhancing microwave absorption by conduction and polarization loss balance

As a transparent semiconductor, indium oxide (In₂O₃) exhibits intrinsically low dielectric parameter, rendering it ineffective for microwave absorption. Overcoming its inherent wide bandgap and limited dielectric loss to achieve effective microwave absorption presents a significant challenge. Herein, a lattice defect engineering strategy is proposed to construct oxygen vacancy-rich indium oxide (In₂O_3−x) and carbon-doped indium oxide (In₂O_3−x/C) particles with extrinsic defects. This approach achieves a breakthrough in the effective absorption bandwidth (EAB) of pristine In₂O₃, expanding it from 0 to 3.7 GHz. Furthermore, this study discovers that higher 1,2-benzisothiazoline-3-one dosages increase the oxygen vacancy concentration in In₂O_3−x/C, which is crucial for the material to exhibit microwave absorption capabilities. In particular, the In₂O_3−x/C-0.3 sample demonstrates enhanced microwave absorption through the synergistic effect of carbon doping, achieving a broad EAB of 5.0 GHz. Density Functional Theory calculations further reveal that the introduction of oxygen vacancies and carbon doping can optimize the band structure, reduce the bandgap and induce internal charge redistribution, thereby enhancing the conductive and polarization losses. This research is expected to open up a new avenue in the field of microwave absorption for In₂O₃ applications.