Voltage-dependent resistance of undoped rutile, TiO2, ceramics

Lightly reduced rutile ceramics are n-type semiconductors whose resistance increases reversibly by 1–2 orders of magnitude, depending on temperature, on application of a small dc bias of 10–100 V cm−1. A similar effect is seen on changing the oxygen partial pressure surrounding the sample during impedance measurements and the bias dependence is attributed to changes in the equilibria between various ionised oxygen species adsorbed on sample surfaces, leading to changes in the mobile electron concentration in the sample bulk. The increase in resistance of n-type TiO2 with dc bias mirrors the decrease in resistance seen with p-type semiconductors such as acceptor-doped BaTiO3 and represents an effect, which has certain memristive characteristics but also significant differences