For AgSnO2 contact materials, Ag has good electrical conductivity while SnO2 has high thermal stability. However, SnO2, despite of a semiconductor with a wide band gap, is nearly a non-conducting compound, leading to an increase in the resistance of AgSnO2. By doping SnO2 with other conductive metals, the electrical properties of AgSnO2 can be effectively improved. In the present theoretical study based on the first-principles, the electric structure of SnO2 doped with La Ce and Nd was analyzed, and the crystal structure, band structure and density of states of the intrinsic SnO2 and doped SnO2, were compared. The crystal structure shows that the lattice distortion caused by the rare earth is related to the covalent radius of the doping atoms. The conduction band of the doped SnO2 shifts to the lower energy level, as indicated by the band structure, resulting in a narrow bad gap and improved electrical conductivity. SnO2 doped with La has a minimum band gap. The density of states reveals that the unique electronic state on f-orbits of the rare earth has a great contribution to the conduction band at the Fermi level. The density of states of La-doped SnO2 is the maximum. |