The present work considers the effect of oxygen activity on the chemical diffusion coefficient in terms of defect disorder and the related semiconducting properties. The transport kinetics under a chemical potential gradient in amphoteric oxide semiconductors exhibits a complex dependence within the n–p transition. It is shown that the effect may be related to the concentration of electronic charge carriers. The derived analytical form explains the empirical relationship between the chemical diffusion coefficient and oxygen activity reported for TiO2.
FujishimaA. and HondaK.: Nature, 1972, 238, 37–38.
2.
HepelT., HepelM. and OstryoungR. A.: J. Electrochem. Soc., 1982, 129, 1231–1241.
3.
KhanS., Al-ShahryM. and InglerW. B.: Science, 2002, 297, 2243–2244.
4.
NakamuraR., TanakaY. and NakatoY.: J. Phys. Chem. B, 2004, 108B, 10617–10620.
5.
BakT., NowotnyJ., RekasM. and SorrellC. C.: Int. J. Hydrogen Energy, 2002, 27, 991—1022.
6.
NowotnyJ., BakT., NowotnyM. K. and SorrellC. C.: Phys. Stat. B, 2005, 242B, R91—R93.
7.
ChildsP. E. and WagnerJ. B., Jr: in ‘Heterogeneous kinetics at elevated temperatures’, (ed. BeltonG. R. and WorrellW. L.), 264–342; 1970, New York, Plenum Press.
8.
KofstadP.: ‘Nonstoichiometry, diffusion and electrical conductivity in binary metal oxides’: 1972, New York, Wiley.
9.
StonehamA. M.: Phys. Today, Jan. 1980, 34–42.
10.
KroegerF. A.: ‘The chemistry of imperfect crystals’: 1964, Amsterdam, North Holland.
11.
NowotnyM. K., BakT., NowotnyJ. and SorrellC. C.: Phys. Stat. B, 2005, 242B, R88—R90.
12.
NowotnyM. K.: ‘Defect disorder, electrical properties and chemical diffusion of TiO2 single crystal’, PhD thesis, School of Materials Science and Engineering, University of New South Wales, Sydney, 2006.
13.
NowotnyJ., SorrellC. C., BakT. and SheppardL. R.: in ‘Materials for energy conversion devices’, 84–116; 2005, Cambridge, Woodhead.
14.
WagnerC.: Z. Physik. Chem., 1933, B21, 25–35.
15.
WagnerC.: Progr. Solid State Chem., 1975, 10, 3–16.
16.
KofstadP.: ‘High temperature corrosion’, 167; 1988, Amsterdam, Elsevier.
17.
BakT., NowotnyJ., RekasM. and SorrellC. C.: J. Phys. Chem. Solids, 2003, 64, 1057–1067.