Electronic Conductivity and Stability of Doped Titania (Ti1-XMXO2, M = Nb, Ru, and Ta)-A Density Functional Theory-Based Comparison

The structure, electrical conductivity, and stability of Nb-. Ru-, and Ta-doped mania were compared by density functional theory Both anatase and rutile structures were investigated Doping causes lattice expansion in all cases. The mechanism by which Ru-doping induces electrical conductivity in mania differs from those by Ta- and Nb-doping Ru-doping fills the Mania band gap primarily with its own d-electrons. On the other hand, Ta- and Nb-doping shift the Fermi level to the originally unfilled conduction states. Substitution free energy calculations indicate that a uniform Ti0 75M0 25O2 solution is favorable for Nb- and Ta-doping but unfavorable for Ru-doping. In addition, we also considered the effect of dopant concentration on the electrical conductivity of doped titania in the rutile phase For Nb- and Ta-doping, increasing dopant concentration above mole fractions of 0 0625 and 0 125, respectively, gives diminished increment in Fermi level electron density. On the other hand, electron density at the Fermi level of Ru-doped ruffle is more linearly dependent on Ru mole fraction