Grain refining effect of calcium dopants on gas-sensing properties of electrospun α-Fe2O3 nanotubes

Here we report a type of electrospun α-Fe2O3 nanotubes doped with different mole percentage of calcium (Ca) elements and the grain refining effect of Ca on the properties of the obtained samples. Results show that the microstructures and morphologies of the as-prepared α-Fe2O3 nanotubes are significantly affected by doping contents (1-15 mol%). With increasing Ca doping content, the grain size of α-Fe2O3 nanotubes decreases monotonously (named “grain refining effect”). This is due to the low calcination temperature and a large mismatch between the radii of Ca2+ and Fe3+ ions. Moreover, gas-sensing tests show that the Ca-doped α-Fe2O3 nanotube based sensors exhibit enhanced gas-sensing properties toward both ethanol and acetone. At an optimal operating temperature of 200 °C, 7 mol% Ca-doped sensors present the highest response value to ethanol (26.8/100 ppm) and acetone (24.9/100 ppm) with a fast response/recovery rate. Furthermore, a possible gas-sensing mechanism is proposed, which suggests the grain refining effect of Ca dopants plays a dominant role in improving the sensing performances of α-Fe2O3 nanotubes.