Phase transformation (cubic to rhombohedral): the effect on the NO2 sensing performance of Zn-doped flower-like In2O3 structures

Abstract

Cubic In2O3 (bcc-In2O3) was transformed into a mixture of bcc-In2O3 and rhombohedral In2O3 (rh-In2O3) by Zn doping. The Zn-doped flower-like In2O3 structures consisted of many thin sheets with a length of 0.4–1 μm, and cubes with a length of 200 nm, while the size of the microflowers was 1–3.5 μm. The Zn doping concentration significantly affected the phase transformation and the overall morphology of In2O3. Furthermore, the analysis of N2 adsorption–desorption measurements showed that the Zn-doped flower-like In2O3 structures (sample S5) adsorbed the largest amount of N2 and had the biggest surface area (46.41 m2 g−1), which contributed to an improvement in gas sensing performance. Finally, sensors based on the mixture of bcc- and rh-In2O3 structures exhibited a much higher response to NO2 than the pure bcc-In2O3 (sample S1), and the Zn-doped flower-like In2O3 structures (sample S5) exhibited the highest response of 27.4 ± 2.5 for 5 ppm NO2. Thus, the gas sensing performance of In2O3 was enhanced significantly by the phase transformation.