Charge compensation in iron-doped rutile

Andersson, Per‐Olof; Kollberg, E.; Jelenski, A.

doi:10.1088/0022-3719/7/10/014

Cited by 19 publications

(9 citation statements)

References 25 publications

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“…It is well-established that the principle point defects in rutile TiO 2 at all temperatures and O 2 partial pressures are the O vacancy and the Ti interstitial. − However, in SnO 2 , there is a significant concentration of intrinsic Sn vacancies . Thus either the interstitial or vacancy diffusion mechanism could conceivably operate in the Ti x Sn 1− x O 2 materials studied here.…”

Section: Discussionmentioning

confidence: 92%

Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Palgrave

Bourlange

Payne

et al. 2009

Crystal Growth & Design

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Oxygen plasma-assisted molecular beam epitaxy was used to grow layers of SnO 2 on single-crystal rutile TiO 2 (110) substrates. Surface composition was studied by X-ray photoelectron spectroscopy, whereas secondary ion mass spectrometry was used to determine the depth distribution of Sn and Ti. For substrate temperatures below 600 °C, SnO 2 grows as an epitaxial film on top of the TiO 2 , but at higher temperatures there is evidence for pronounced interdiffusion between the substrate and the epilayer. At growth temperatures above 775 °C the Sn diffuses rapidly into the substrate to give Sn-doped TiO 2 rather than a distinct SnO 2 epilayer. The films were all highly (110) oriented but the lattice parameter of the deposited film decreased with increasing growth temperature, consistent with the formation of Ti x Sn 1-x O 2 solid solutions through interfacial solid-state reaction in a narrow temperature regime between 750 and 775 °C.

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Section: Discussionmentioning

confidence: 92%

Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Palgrave

Bourlange

Payne

et al. 2009

Crystal Growth & Design

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“…Bates et al did a computational study of the mechanisms of proton diffusion in rutile and found results in good agreement with the reported experimental measurements. Several spectroscopic techniques have also revealed hydrogen in single crystal TiO 2 and Fe-doped TiO 2 , − with consensus that hydrogen is present as OH − ions.…”

Section: Hydrogen In Tio2mentioning

confidence: 99%

Hydration of Rutile TiO₂: Thermodynamics and Effects on n- and p-Type Electronic Conduction

et al. 2010

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The bulk conductivity of polycrystalline 1 mol-% Fe-doped rutile TiO2 has been measured as a function of p H2O and temperature under oxidizing and reducing conditions. From the p H2O-dependency of the conductivity, it is concluded that protons are significant positive defects and, furthermore, that mixed p-type electronic and protonic, and n-type electronic conduction dominate under oxidizing and reducing conditions, respectively. H2O/D2O isotope exchange confirmed that protons are significant charge carriers under wet oxidizing conditions below approximately 600 °C. Thermodynamic parameters for the hydration reaction were obtained by modeling the experimental p H2O and temperature dependencies, assuming that the acceptor dopant (Fe3+) is charge compensated by protons and oxygen vacancies, and from ab initio density functional theory (DFT) calculations. The experimental data yield standard enthalpy changes of hydration of −130 ± 16 kJ/mol, whereas the calculated values are somewhat more negative; −155 to −162 kJ/mol. Based on such favorable thermodynamics of hydration, it is concluded that protons will be the dominating positive defect in TiO2 under most conditions of practical interest.

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“…Therefore, we conclude that in our samples the iron impurities play the most important role in the breakdown phenomenon, facilitating the tunneling of electrons from solution through either a narrow or a thick space charge region and into the conduction band. This tunneling of electrons is likely to occur via iron precipitates that are known to form on lattice defects in TiO2 (12,13). In fact, in our Fe-doped single crystal samples, reddishbrown iron precipitates were visually observed.…”

Section: Current-potential Characteristics--figuresmentioning

confidence: 72%

“…From EPR studies on Fe-doped single crystal TiOs, Andersson (12) showed that strong reduction, made in Vacuum, probably causes a transformation of Fe a+ into Fe 2+ ions. These Fe ~+ ions, will preferentially occupy the Fe e+ level near the conduction band that is vacant before the reduction treatment.…”

Section: Resultsmentioning

confidence: 99%

Photoelectrolysis of Water with Natural Mineral TiO2 Rutile Electrodes

Julião¹,

Decker²,

Abramovich³

1980

J. Electrochem. Soc.

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Natural mineral rutile (TiO2) was studied as anode for photoelectrolysis of water. Both its photoelectrochemical behavior and semiconducting properties are examined in comparison with those of Fe-doped synthetic single crystal TiO2, the latter independently studied to simulate the high impurity content existent in the mineral. The natural and synthetic Fe-doped TiO2 electrodes showed a performance comparable to that of arc-plasma sprayed raw rutile, including a low breakdown potential. Flatband potentials and donor densities were determined from Mott-Schottky plots and evidence for deep and shallow donors is discussed. Photoresponse measurements allowed us to verify the influence of the iron impurities on the performance of such electrodes.The photoelectrolysis of water has been investigated by several authors (1-7) in the last few years. Electrodes of polyerystalline TiO2 made by hot-pressing powdered rutile (2), by oxidation of metal foils (2-4), and by chemical vapor deposition (CVD) (5, 6) show a behavior similar to that of single crystal TiO., ( 7) and have the advantage of being easier to prepare. Until now, little attention has been paid to the semiconductor properties of natural TiO2 rutile crystals, perhaps because these minerals are usually impure (8). However, it has been recently shown that impure polycrystalline TiO2 electrodes, prepared by arcplasma sprayed raw rutile powder (9), behave similarly to other polycrystalline ones with respect to photoeleetrolysis. In the present paper we report the photoelectrochemical behavior of electrodes made either of single crystal or polycrystalline natural TiO2, obtained from mines located in different regions of Brazil. These electrodes showed a performance comparable to that of synthetic single crystal or other polycrystalline TiO2 electrodes. The results demonstrate the possibility of using low cost raw materials in primitive form for photoelectrolysis of water.Since large amounts of iron impurities were detected by x-ray analysis in the mineral samples, their effect on the performance of the photoelectrolytic cell is discussed by comparing the behavior of the natural futile electrodes with that of two intentionally Fe-doped TiO2 synthetic single crystal electrodes. Experimental ProcedureSample characterization and heat-treatments.--Sam-* Electrochemical Society Student Member. ** Electrochemical Society Active Member.

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Charge compensation in iron-doped rutile

Cited by 19 publications

References 25 publications

Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Hydration of Rutile TiO₂: Thermodynamics and Effects on n- and p-Type Electronic Conduction

Photoelectrolysis of Water with Natural Mineral TiO2 Rutile Electrodes

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Charge compensation in iron-doped rutile

Cited by 19 publications

References 25 publications

Interfacial Diffusion during Growth of SnO2(110) on TiO2(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Interfacial Diffusion during Growth of SnO2(110) on TiO2(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Hydration of Rutile TiO2: Thermodynamics and Effects on n- and p-Type Electronic Conduction

Photoelectrolysis of Water with Natural Mineral TiO2 Rutile Electrodes

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Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Interfacial Diffusion during Growth of SnO₂(110) on TiO₂(110) by Oxygen Plasma Assisted Molecular Beam Epitaxy

Hydration of Rutile TiO₂: Thermodynamics and Effects on n- and p-Type Electronic Conduction