The Location of M(IV) Dopants in Hematite
EMSL Project ID
1648
Abstract
Redox reactions that occur on iron oxides are critical in biogeochemical cycles and are potentially important in controlling corrosion at iron surfaces and for degrading organic pollutants. The rates of many reduction reactionsinvolving predominantly Fe(III)-containing oxides can be increased by introducing Fe(II) into the oxide. One way to do this in hematite, alpha-Fe2O3, is to introduce M(IV) impurities into the sample (i.e., dope with M(IV)). If the M(IV) cations are incorporated into the lattice, they may introduce energy levels into the hematite electronic structure which could reduce the rate of reduction reactions by trapping electrons. The overall effect of the M(IV) ions on the rate of reduction reactions on hematite, then, is not clear. It is important to understand how dopants affect the reactivity of iron oxides towards reduction reactions since impurities that act as dopants will likely be incorporated into these oxides in natural systems. We propose to use the Auger Electron and X-ray Photoelectron Spectroscopy facilities at EMSL to determine the dopant concentration at various locations throughout our hematite samples, most importantly at the surface, in the bulk of the material (after sputtering and/or polishing) and at grain boundaries. This information will allow us to conclude whether the different behavior we see for the Ti(IV)-doped hematite is due to the presence of energy levels introduced by the incorporation of Ti(IV) ions into the oxide lattice or whether it is due to some other electronic or structural change associated with the presence of Ti(IV) ions at the hematite surface or grain boundaries.
Project Details
Project type
Exploratory Research
Start Date
1999-08-16
End Date
2001-07-01
Status
Closed
Released Data Link
Team
Principal Investigator