Fig. 1.
Comparison between anatase- and rutile-predominated undoped n-type TiO2 nanopowders obtained by flame spray synthesis (FSS): a X-ray diffraction patterns, b SEM images, c resistive-type response R 0/R to hydrogen at 300 °C, d Nyquist plots recorded at 400 °C illustrating imaginary part of impedance Z″ as a function of its real part Z′: f R, rutile content; d A, diameter of anatase crystallite; d R, diameter of rutile crystallite; R 0, electrical resistivity in the reference atmosphere (air); R, electrical resistivity under exposure to detected gas; σ, electrical conductivity; C, capacitance and ε, dielectric constant