Here we report a type of electrospun alpha-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 alpha-Fe2O3 nanotubes are significantly affected by doping contents (1-15 mol%). With increasing Ca doping content, the grain size of alpha-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 alpha-Fe2O3 nanotube based sensors exhibit enhanced gas-sensing properties toward both ethanol and acetone. At an optimal operating temperature of 200 degrees 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 alpha-Fe2O3 nanotubes. (C) 2016 Elsevier B.V. All rights reserved.