Untersuchung der Fehlordnung von TiO<sub>2</sub> (Rutil) mit Hilfe von Leitfähigkeits‐ und Überführungsmessungen

Singheiser, L.; Auer, W.

doi:10.1002/bbpc.19770811111

Cited by 21 publications

(17 citation statements)

References 13 publications

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“…Effect of Oxygen Activity. The literature reports on electrical properties of TiO 2 at elevated temperatures concentrate on the effects of oxygen activity and temperature on the electrical properties, − including electrical conductivity, thermoelectric power, and Hall effect. However, the vast majority of the reported data concerns the electrical conductivity.…”

Section: Brief Literature Overviewmentioning

confidence: 99%

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

2006

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The present work reports the electrical properties of high-purity single-crystal TiO(2) from measurements of the electrical conductivity in the temperature range 1073-1323 K and in gas phases of controlled oxygen activities in the range 10(-13) to 10(5) Pa. The effect of the oxygen activity on the electrical conductivity indicates that oxygen vacancies are the predominant defects in the studied ranges of temperature and oxygen activities. The electronic and ionic lattice charge compensations were revealed at low and high oxygen activities, respectively. The determined semiconducting quantities include: the activation energy of the electrical conductivity (E(sigma) = 125-205 kJ.mol(-1)), the activation energies of the electrical conductivity components associated with electrons (E(n) = 218 kJ.mol(-1)), electron holes (E(p) = 34 kJ.mol(-1)), and ions (E(i) = 227 kJ.mol(-1)), and the enthalpy of motion for electronic defects (DeltaH(m) = 4 kJ/mol). The electrical conductivity data are considered in terms of the components related to electrons, holes, and ions. The obtained data allow the determination of the n-p demarcation line in terms of temperature and oxygen activities. The band gap determined from the electronic component of the electrical conductivity is 3.1 eV.

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Section: Brief Literature Overviewmentioning

confidence: 99%

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

2006

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“…(iv) what the extent of the ionic contribution to the total conductivity is. 13,[28][29][30] In our earlier work on undoped single crystal TiO 2Àd , 5 we have found that the oxide remains oxygen-deficient all the way up to a O 2 = 1 with the majority type of disorder changing…”

Section: Introductionmentioning

confidence: 94%

Electrical conductivity and oxygen nonstoichiometry of acceptor (Ga)-doped titania

Lee

Yoo

2008

Phys. Chem. Chem. Phys.

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Electrical conductivity and oxygen nonstoichiometry (delta) have been measured, respectively, by a dc 4-probe technique and coulometric titrometry on the system of polycrystalline Ti0.99Ga0.01O1.995-delta against oxygen activity in the range of -20 < log aO2 < or = 0 at different temperatures in the range of 1073 < or =T/K < or = 1373. It is found that isothermal conductivity varies as sigma alpha aO2m with m approximately -1/4, -1/5, -1/4, +1/4, in order of increasing aO2, finally exhibiting an n-type (m = -1/4) to p-type (m = +1/4) transition crossing the stoichiometric composition (delta = 0), in perfect agreement with the oxygen nonstoichiometry variation. The electrical conductivity and oxygen nonstoichiometry isotherms are combined to evaluate the ionic partial conductivity and transference number, the intrinsic electronic excitation equilibrium constant, and eventually both mobilities of electrons and holes without employing any assumption at all. The partial molar enthalpy and entropy of the component oxygen are also evaluated as functions of nonstoichiometry.

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“…Most of the reported data on the properties of TiO 2 correspond to the operational equilibrium . The related properties, such as the absolute values of the electrical conductivity, may differ substantially. − The difference is related to different oxygen activity in the oxide lattice and the associated concentration of titanium vacancies. The properties of TiO 2 exhibit reproducible properties only when the studied specimens are in full equilibrium.…”

Section: Brief Overview Of Literature Datamentioning

confidence: 99%

Electrical Conductivity, Thermoelectric Power, and Equilibration Kinetics of Nb-Doped TiO₂

et al. 2016

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This work considers the equilibration kinetics of Nb-doped TiO2 single crystal (0.066 atom % Nb) during oxidation and reduction within a wide range of temperature (1073-1298 K) and oxygen activity (10(-14)-10(5) Pa). The associated semiconducting properties were determined using simultaneous measurements of both electrical conductivity and thermoelectric power. It is shown that the chemical diffusion coefficient in the strongly reducing regime, p(O2) < 10(-5) Pa, is 4 orders of magnitude larger than that in the reducing and oxidizing regimes, 10 Pa < p(O2) < 22 kPa. The derived theoretical model considers the gas/solid kinetics for the TiO2/O2 system in terms of two diffusion regimes: the fast regime related to fast defects (oxygen vacancies and titanium interstitials) and leading to quasi-equilibrium, and the slow regime associated with slow defects (titanium vacancies) resulting in the gas/solid equilibrium. It has been shown that incorporation of donor-type elements, such as niobium, and imposition of oxygen activity above a certain critical value, results in a substantial reduction in the concentration of high mobility defects and leads to slowing down the equilibration kinetics. In consequence, the fast kinetic regime is not observed. Comparison of the kinetic data for Nb-doped TiO2 single crystal (this work) and polycrystalline Nb-doped TiO2 (reported before) indicates that the gas/solid kinetics for the polycrystalline specimen at higher oxygen activities is rate controlled by the transport of oxygen within individual grains.

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Untersuchung der Fehlordnung von TiO₂ (Rutil) mit Hilfe von Leitfähigkeits‐ und Überführungsmessungen

Cited by 21 publications

References 13 publications

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

Electrical conductivity and oxygen nonstoichiometry of acceptor (Ga)-doped titania

Electrical Conductivity, Thermoelectric Power, and Equilibration Kinetics of Nb-Doped TiO₂

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Untersuchung der Fehlordnung von TiO2 (Rutil) mit Hilfe von Leitfähigkeits‐ und Überführungsmessungen

Cited by 21 publications

References 13 publications

Electrical Properties and Defect Chemistry of TiO2Single Crystal. I. Electrical Conductivity

Electrical Properties and Defect Chemistry of TiO2Single Crystal. I. Electrical Conductivity

Electrical conductivity and oxygen nonstoichiometry of acceptor (Ga)-doped titania

Electrical Conductivity, Thermoelectric Power, and Equilibration Kinetics of Nb-Doped TiO2

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Untersuchung der Fehlordnung von TiO₂ (Rutil) mit Hilfe von Leitfähigkeits‐ und Überführungsmessungen

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

Electrical Conductivity, Thermoelectric Power, and Equilibration Kinetics of Nb-Doped TiO₂