Electrical properties of TiO2: equilibrium vs dynamic electrical conductivity

Abstract

The present work reports semiconducting properties of high purity TiO 2 determined in the gas/solid equilibrium, as well as during controlled heating and cooling in the range 300-1,273 K. The activation energy of the electrical conductivity is considered in terms of the activation enthalpy of the formation of ionic defects and the activation enthalpy of the mobility of electronic defects. These data, determined from the dynamic electrical conductivity experiments, are compared to the electrical conductivity data determined in equilibrium. It is shown that only the equilibrium electrical conductivity data for high-purity TiO 2 are well defined. It is shown that the activation energy of the electrical conductivity determined in equilibrium differs substantially from that for the dynamic electrical conductivity data during cooling and heating. It is concluded that the formation enthalpy term determined from the dynamic conductivity data is determined by the heating/cooling rate rather than materials' properties.

Resolving Bulk and Grain Boundary Transport Properties of TiO2 Thin Films Enabled by Laser‐Induced Anisotropic Morphology

“…Therefore, we suppose that the films were intrinsically doped by donor‐like oxygen vacancies that were produced during the post‐laser annealing and subsequently quenched upon the fast cooling (100 °C min −1 ) to ambient temperature. These oxygen vacancies remained quenched in the films during the impedance measurements between 300 and 450 °C because of the slow oxygen exchange kinetics at these temperatures 22–24…”

An Investigation of Electro-deoxidation Process for Producing Titanium from Dense Titanium Dioxide Cathode

“…At the present experimental temperature, the electric resistivity of polycrystalline TiO 2 (measured in Ar atomsphere) is as high as 10 4 Ω·cm [20], while it is 10 −1 to 10 1 Ω·cm for TiO 2-x [21]. This means, at the initial stage of the deoxidation, the high resistance of cathode would result in large voltage drop within the cathode.…”

Anomalous Electronic and Protonic Conductivity of 2D Titanium Oxide and Low‐Temperature Power Generation Using Its Protonic Conduction

“…At 300 °C, it was about 0.2 S cm −1 , which is a huge value considering the fact that of 3D TiO 2 is below 10 −10 S cm −1 at that temperature. [39,40] Correspondingly, the activation energy (E a ≈ 0.73 eV) of 2D titanium-oxide was lower than the reported value of 3D TiO 2 (anatase ≈ 1.72 eV). [39,40] This enhanced electronic conduction is because it is much easier for the following defect reaction to occur in 2D titanium-oxide (oxygen-vacation formation reaction, and Kröger-Vink notation is used for point defects).…”

“…As a result, the simulated average formation energy was too small to be <1 eV as expected, showing the reason why 2D titanium-oxide is conductive and has low activation energy (note that that of 3D TiO 2 is about 4eV). [40] On the other hand, if electrons are produced by the oxygen-vacation formation reaction, electronic conduction should rely on exponent -1/6 of oxygen partial pressure (σ ∝ P O2 −1/6 , P O2 is the oxygen partial pressure) according to the defect chemistry of the reaction. [41,42] Indeed, the conductivity measured as a function of P O2 similarly depends on that partial pressure, as seen in Figure 4b (note that the data was measured under the different P O2s controlled by the mixture gases of dry N 2 and O 2 ).…”