Electrode effects in dielectric spectroscopy measurements on (Nb+In) co-doped TiO2.

Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO₂. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and alternating current (ac) conductivity of co-doped (Nb+In)TiO₂ as a function of electrode type, sample thickness, and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four-contact van der Pauw direct current conductivity measurements and bulk conductivity values extracted from two-contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature. [ABSTRACT FROM AUTHOR]