The effect of different crystalline phases of In₂O₃ on the ozone sensing performance

Crystalline phase regulation could optimize the band gap, which has a great impact on the amount of chemisorbed gas molecules on the gas sensing materials. Herein, a facile route of hydrothermal method followed by calcination treatment was used to synthesize cubic bixbyite-type (C-In₂O₃), rhombohedral corundum-type (Rh-In₂O₃) and the mixed phase In₂O₃ (Rh+C-In₂O₃). The band gap of C-In₂O₃ was narrowed to a suitable value (2.38 eV) and the relative percentage of chemisorbed oxygen was enhanced (31.8%). The sensing results to ozone (O₃) indicated that the C-type structure stood out. The gas sensor based on C-In₂O₃ exhibited extraordinary O₃ sensing performances with a response of 5.7 (100 ppb) and an ultralow limit of detection of 30 ppb. The amazing results could be attributed to the narrow band gap and the enrichment of chemisorbed oxygen. This work inspires a new perspective to design highly sensitive and reliable O₃ sensors.