Heterostructure Fe2O3–In2O3 Nanoparticles as Hydrogen Gas Sensor

Fe2O3–In2O3 (9:1 mol.%) heterostructure nanoparticles were prepared by the thermal decomposition of stoichiometric amounts of Fe2C2O4 2H2O and In(OH)3 at 400°C for 20 h. The sample was characterized by x-ray diffraction (XRD), Fourier-transform infrared spectrometry, thermogravimetry–differential thermal analyzer, scanning electron microscopy/transmission electron microscopy, and a superconducting quantum interference device magnetometer. The XRD pattern could be indexed to both the rhombohedral α–Fe2O3 and cubic bixbyite In2O3 phases. This heterostructure system showed ferromagnetic properties (due to the presence of γ–Fe2O3 phase) from 5 to 300 K and a spin-glass-like behavior of magnetization versus temperature under zero-field-cooled and field-cooled conditions. H2 gas-sensing property was observed from 100 ppm to 2 ppm at 200 °C and 250 °C. Response and recovery times were about 275 s and 500 s, respectively, and the sensitivity varied from 2% to 21% as the H2 increased from 2 to 100 ppm. The Ra/Rg varied from 1 to 1.3 and the plot of Ra/Rg versus H2 could be fitted to the sigmoidal logistic function, y = A2 + (A1 − A2) / (1 + (x/x0)p.