Defect structure and DC electrical conductivity of titanium dioxide-niobium dioxide solid solution

The defect structure and the dc electrical conductivity of TiO{dollar}sb2{dollar}-NbO{dollar}sb2{dollar} solid solution have been studied by using time-of-flight neutron diffraction, Nb K-edge x-ray absorption spectroscopy, and dc electrical conductivity measurement as a function of composition. The oxygen content in the solid solutions was determined using thermogravimetric analysis, and the results of other experiments were analyzed and correlated to establish a defect structure that controls the dc electrical conductivity. The lattice parameters and the interstitial defect occupancy were determined using the Rietveld method applied to neutron diffraction results. The valence and the coordination state of Nb ions were determined through XANES and EXAFS analyses of Nb K-edge x-ray absorption data.; The formation of Nb-Nb pairs postulated by other researchers was directly observed by Nb K-edge EXAFS analysis. The formation of Nb-Nb pairs was also noticed in the results of neutron diffraction analysis and dc electrical conductivity measurement. A conductivity maximum was observed at Nb{dollar}sb{lcub}0.1{rcub}{dollar}Ti{dollar}sb{lcub}0.9{rcub}{dollar}O{dollar}sb2{dollar}, after which the conductivity decreases with increasing Nb concentration. The decreasing conductivity with increasing Nb concentration is attributed to the pair formation, by which charge carriers are localized between the two Nb ions.