Microstructure and electrical properties of Nb2O5 doped titanium dioxide

The present work attempts to investigate the sintering characteristics, grain boundary morphology and electric conductivity of Nb2O5 doped TiO2 semiconductor ceramics. X-ray diffraction results showed evidence of a second phase beside the rutile TiO2 when Nb2O5 exceeds 0.7 mol%. SEM images showed that Nb2O5 doping can lowers the sintering temperature of TiO2, although not significantly. Lattice images of the grain boundary morphology obtained by high resolution transmission electron microscopy revealed defects introduced from the doping. Grain boundaries vary from amorphous to a faceted structure. Finally, electrical conductivity measurements showed that the grain boundary resistance is greatly reduced at high temperature.