Advertisement

Ionics

, Volume 10, Issue 3–4, pp 166–176 | Cite as

Thermoelectric power of mixed electronic-ionic conductors II. Case of titanium dioxide

  • T. Bak
  • J. Nowotny
  • M. Rekas
  • C. C. Sorrell
Article

Abstract

The purpose of the present work is the determination of the thermopower components corresponding to different charge carriers (electrons, electron holes and ions) for TiO2 and the use of these data for evaluation of the effect of symmetry between these two properties. The procedure of the determination of these components was based on the following two approximations:
  • The first approximation is based on a symmetrical model assuming a consistency between thermopower and electrical conductivity within the n-p transition (minimum of electronic component of the electrical conductivity corresponds to zero value of the electronic component of thermopower).

  • The second approximation is based on the apparent asymmetry between thermopower and electrical conductivity within the n-p transition as determined from the first approximation.

The analysis, based on the data of the electronic components of thermopower and electrical conductivity for TiO2 single crystal, results in the band gap (using the Jonker formalism). The determined band gap is equal to 2.77 eV and 2.57 eV at the first and the second approximations, respectively, while the band gap determined from the experimentally measured data is equal 3.35 eV. These values are consistent with the band gap determined from the data of electrical conductivity corresponding to the n-p transition point (Eg=3.16 eV) and for the data measured experimentally and those free of the ionic conductivity component (Eg=2.79 eV). The obtained results indicate that thermopower and electrical conductivity most likely exhibit the effect of symmetry.

Keywords

TiO2 Titanium Analytical Chemistry Dioxide Electrical Conductivity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Nomenclature

A

Kinetic constant

e

Elementary charge [1.602×10−19 C]

Eg

Band gap [eV]

k

Boltzmann constant [8.6167×10−5 eV K−1]; [1.380×10−23 J K−1]

n

Concentration of electrons [m−3]

N

Density of states [m−3]

q

Heat of transfer [J]

p

Concentration of electron holes [m−3]

p(O2)

Oxygen partial pressure [Pa]

S

Thermopower (Seebeck coefficient) [V K−1]

So(O2)

Standard entropy of oxygen [J mol−1 K−1]

s

Partial molar entropy [J mol−1 K−1]

s*

Transported entropy [J mol−1 K−1]

t

Transference (transport) number

T

Absolute temperature [K]

z

Valency

μ

Mobility [m2 V−1 s−1]

σ

Electrical conductivity [Θ−1m−1]

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. [1]
    A. Fujishima, K. Honda, Nature238, 37 (1972).CrossRefGoogle Scholar
  2. [2]
    A. Fujishima, K. Hashimoto, T. Watanabe, TiO2 Photocatalysis, Published by: BKC, Inc., Tokyo, 2001.Google Scholar
  3. [3]
    T. Ohnishi, Y. Nakato and H. Tsubomura, Ber. Bunsen Ges.79, 523 (1975).Google Scholar
  4. [4]
    J.G. Mavroides, J.A. Kafalas and D.F. Kolesar, Appl. Phys. Lett.28, 241 (1976).CrossRefGoogle Scholar
  5. [5]
    A.J. Nozik, Nature257, 383 (1975).CrossRefGoogle Scholar
  6. [6]
    H. Morisaki, T. Watanabe, M. Iwase and K. Yazawa, App. Phys. Lett.29, 338 (1976).CrossRefGoogle Scholar
  7. [7]
    D. Laser and A.J. Bard, J. Electrochem. Soc.123, 1027 (1976).Google Scholar
  8. [8]
    P.D. Fleischauer and J.K. Allen, J. Phys. Chem.82, 432 (1978).CrossRefGoogle Scholar
  9. [9]
    A.K. Ghosh and H.P. Muruska, J. Electrochem. Soc.124, 1516 (1977).Google Scholar
  10. [10]
    J.F. Houlihan, D.B. Armitage, T. Hoovler, D. Bonaquist, D.P. Madacsi and L.N. Mulay, Mat. Res. Bull.13, 1205 (1978).CrossRefGoogle Scholar
  11. [11]
    J. Akikusa and S.U.M. Khan, Int. J. Hydrogen Energy22, 875 (1997).Google Scholar
  12. [12]
    P. Kofstad, Nonstoichiometry, Diffusion and Electrical Conductivity of Binary Metal Oxides, Wiley, New York, 1972.Google Scholar
  13. [13]
    J. Yahia, Phys. Rev.130, 1711 (1963).CrossRefGoogle Scholar
  14. [14]
    J.-F. Baumard, E. Tani, Phys. Stat. Solidi (a)39, 373 (1977).Google Scholar
  15. [15]
    F. Millot, M.G. Blanchin, R. Tetot, J-F. Poumellec, C. Picard, B. Touzelin, Progr. Solid State Chem.17, 263 (1987).CrossRefGoogle Scholar
  16. [16]
    J. Nowotny, M. Radecka, M. Rekas, J. Phys. Chem. Solids58, 927 (1997).Google Scholar
  17. [17]
    J. Nowotny, M. Radecka, M. Rekas, S. Sugihara, E.R. Vance, W. Weppner, Ceram. Intern.24, 571 (1998).Google Scholar
  18. [18]
    T. Bak, J. Nowotny, M. Rekas, C.C. Sorrell, J. Phys. Chem. Solids64, 1043 (2003).Google Scholar
  19. [19]
    T. Bak, J. Nowotny, M. Rekas, C.C. Sorrell, J. Phys. Chem. Solids64, 1057 (2003).Google Scholar
  20. [20]
    T. Bak, J. Nowotny, M. Rekas, C.C. Sorrell, J. Phys. Chem. Solids64, 1069 (2003).Google Scholar
  21. [21]
    T. Bak, J. Nowotny, M. Rekas, C.C. Sorrell, Ionics, Part I, this issue.Google Scholar
  22. [22]
    T. Bak, J. Nowotny, M. Rekas, C.C. Sorrell, Ionics, Part III, this issue.Google Scholar
  23. [23]
    P.H. Sutter, Thermoelectricity, Chapter 7, Interscience, New York, 1961.Google Scholar
  24. [24]
    I. Barin, Thermochemical Data of Pure Substances, Part 2, VCH, Weinheim, 1989, p. 1093.Google Scholar
  25. [25]
    H.-I. Yoo, J-H. Hwang, J. Phys. Chem. Solids53, 973 (1992).Google Scholar
  26. [26]
    G.H. Jonker, Philips Res. Rep.23, 131 (1968).Google Scholar

Copyright information

© IfI - Institute for Ionics 2004

Authors and Affiliations

  • T. Bak
    • 1
  • J. Nowotny
    • 1
  • M. Rekas
    • 1
  • C. C. Sorrell
    • 1
  1. 1.School of Materials Science and EngineeringThe University of New South WalesSydney

Personalised recommendations