Charge transport in polycrystalline titanium dioxide☆

Бак, Т.; Burg, Thomas P.; Kang, Suk–Joong L.; Nowotny, Janusz; Rękas, M.; Sheppard, L. R.; Sorrell, Charles C.; Vance, E. R.; Yoshida, Yasuo; Yamawaki, Michio

doi:10.1016/s0022-3697(03)00005-2

Cited by 30 publications

(26 citation statements)

References 8 publications

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“…The formation of these defects have been already postulated before [5][6][7][8]. So far, however, the effects related to the formation of these defects were observed for TiO 2 single crystal only [4].…”

Section: Introductionmentioning

confidence: 78%

Electrical properties of polycrystalline TiO2. Prolonged oxidation kinetics

Nowotny

Бак

Burg

2007

Ionics

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The equilibration kinetics for polycrystalline TiO 2 was monitored during prolonged oxidation at 1,323 K and p(O 2 ) = 75 kPa using the measurements of the electrical conductivity and thermoelectric power. The determined kinetic data indicate the presence of two kinetics regimes; the Regime I (rapid kinetics) and the Regime II (slow kinetics). The prolonged oxidation of TiO 2 is considered in terms of the formation of Ti vacancies at the surface and their subsequent transport into the bulk. This effect, also observed for TiO 2 single crystal, allows to obtain p-type TiO 2 without the incorporation of acceptor-type foreign ions into the TiO 2 lattice.

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Section: Introductionmentioning

confidence: 78%

Electrical properties of polycrystalline TiO2. Prolonged oxidation kinetics

Nowotny

Бак

Burg

2007

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“…However, there is no agreement with respect to the minimum value of the thermoelectric power, S min . For example, the reported data at 1,273 K are: S = −900 μV/K according to Baumard and Tani [5] and S = −750 μV/K according to Bak et al [8]. While the physical meaning of S min is not well defined (it is influenced by the minority charge carriers), its absolute value for the same compound is expected to be the same in identical conditions of temperature and p(O 2 ).…”

Section: Brief Literature Overviewmentioning

confidence: 99%

“…The thermoelectric power data for TiO 2 at elevated temperatures are scarce and limited to several reports [5][6][7][8]. Moreover, there is no consistency between the reported data.…”

Section: Introductionmentioning

confidence: 99%

Electrical properties of polycrystalline TiO2· Thermoelectric power

Nowotny

Бак

Burg

2007

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The present work determined thermoelectric power for high-purity polycrystalline TiO 2 at elevated temperatures (1,123-1,323 K) and in the gas phase of controlled oxygen activity, 10 −13 Pa < p(O 2 ) < 10 5 Pa. The slope of the thermoelectric power vs log p(O 2 ) is 1/10, instead of 1/6 expected by the theory and observed for TiO 2 single crystal. The discrepancy between the two is considered in terms of the effect of the local grain boundary structure on thermoelectric power. A comparison between the electrical conductivity and thermoelectric power data indicates that the oxygen activity values related to the n-p transition point determined by thermoelectric power are lower than those determined by electrical conductivity.

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“…Significant progress has been made from the first discovery of water splitting on TiO 2 semiconductor electrode [1] in terms of the knowledge of fundamental interfacial processes [2][3][4][5][6][7][8], solar energy conversion efficiency [5], knowledge of point defect equilibria in useful semiconductor materials and their transport properties [9][10][11][12][13][14], methods of photoelectrode synthesis [5,[15][16][17][18][19][20][21][22], and surface treatment techniques [8]. Various enhancements of the original concept of water splitting have been proposed, including dye sensitization [23,24] to expand the range of harnessed solar spectrum and dual semiconductor films [24][25][26] to reduce electron-hole recombination losses.…”

Section: Introductionmentioning

confidence: 99%

“…With the energy bandgap E g =3.055 eV [10], TiO 2 can absorb light with wavelengths shorter than 400 nm and create electron-hole pairs. The valence band edge V VB calculated from the published values of flat band potential V fb = 0.05-0.059 pH [8] (NHE), is V VB = E g + V fb = 2.80 V. The value of V VB is smaller than that for WO 3 (V VB = 3.60 V [28]) and MoO 3 (V VB = 3.21 V [28]).…”

Section: Introductionmentioning

confidence: 99%