Paper SS1-WeM6
Growth and Properties of Iron Oxides on YSZ(001)

Wednesday, October 20, 2010, 9:40 am, Room Picuris

We have used low energy electron microscopy (LEEM) to study in real time the growth of iron oxides on the (001) surface of yttria‑stabilized zirconia - YSZ(001). The FeO_x-YSZ system is currently used as a working material for solar thermochemical splitting of H₂O and CO₂ [1], but little fundamental information is available concerning the structure and composition of the mixed oxides and their surfaces. Upon Fe deposition in ~10^-6 Torr of O₂ background pressure, iron oxides grow on the surface. Observation of low energy electron diffraction (LEED) patterns during growth shows the development of 3 distinct patterns with 12‑fold symmetry, and one pattern with 4‑fold symmetry. Dark field LEEM imaging shows a complicated domain structure where each of the 12‑fold patterns corresponds to 2 or 4 rotationally equivalent domains. Some of the domains overlap laterally, pointing to a layered arrangement of different oxide structures. We use LEEM I‑V and LEED to determine the oxide composition (hematite, magnetite, wüstite) and surface structure, both of which depend on the layer thickness, substrate temperature, and background oxygen pressure.

Sandia National Laboratories is a multi‑program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE‑AC0494AL85000. Funding for this work was provided through Sandia’s LDRD Office.

[1] Diver, R.B., Miller, J.E., Allendorf, M.D., Siegel, N.P., Hogan, R.E., “Solar thermochemical water‑splitting ferrite‑cycle heat engines”, Journal of Solar Energy Engineering, 130 (2008) 041001