The effects of Nb dopant on the lattice structure, thermal, electronic, and optical properties of rutile-phased SnO2 were investigated via ab initio calculations. The corresponding effects of Sb and Ta dopants were also studied for comparison. Results indicated that after SnO2 was doped with Nb, the differences in ionic radii, electron configurations, and electronegativities between the native element and the heterogeneous dopant led to the variations in lattice structure, thermal stability, and electron distribution, while the tetragonal symmetry of the rutile phase is conserved. The partially filled bands around E-f originated from Nb dopant led to the severe enhancement of conductivity, electron excitation in infrared region, and the consequent optical properties except for the band gaps and the selection rule restricting the electron excitation in the visible light region. Therefore, the visible transparency of Nb:SnO2 is expected to be comparable with or even better than Ta:SnO2. (C) 2012 Elsevier B. V. All rights reserved.