Growth of Iron Oxide on Yttria-Stabilized Zirconia by Atomic Layer Deposition

Abstract

The growth and thermal stability of an iron oxide overlayer on yttria-stabilized zirconia (YSZ) have been studied using atomic layer deposition (ALD), mainly in combination with low-energy ion scattering (LEIS). These techniques form a powerful combination, where ALD is designed for controlled (sub)monolayer deposition, while LEIS selectively probes the altered outermost atomic layer. The Fe(acac) 3 precursor reacts already at room temperature with YSZ. The reaction proceeds until saturation, which is characteristic for ALD. After the results of repeated ALD cycles, which consist of Fe(acac) 3 deposition followed by an oxidation treatment, have been studied, a model could be proposed which describes the growth mode of the iron oxide layer on YSZ. Oxidation at temperatures of 800 °C and higher causes a migration of Fe 2 O 3 into the bulk, limiting its usefulness in surface catalytic processes at these temperatures. At 800 °C the diffusion coefficient of Fe in YSZ is determined to be 10 -23 m 2 /s. The reaction mechanism of Fe(acac) 3 with the YSZ surface is studied using infrared diffuse reflectance. The results reveal more than one reaction mechanism, but there seems to be a preference for the reaction via coordinatively unsaturated sites.

Oxidation behaviour of zirconium alloys and their precipitates – A mechanistic study

“…The obtained diffusion coefficients (Table 9) are in a similar range as the one reported by Iltis et al [70]. The zirconia formed during oxidation exhibits much higher diffusion coefficients for iron than sintered yttria stabilized zirconia (single and polycrystalline material [72][73][74]), which are in the range of 10 À21 -10 À27 cm 2 /s when extrapolated to 415°C. The non-surprising difference in iron diffusion coefficient between the different types of yttria stabilized zirconia is the difference between single crystalline material [72] and sintered powder [73,74], for which surface diffusion in the porosity and grain boundary diffusion can be expected.…”

“…The zirconia formed during oxidation exhibits much higher diffusion coefficients for iron than sintered yttria stabilized zirconia (single and polycrystalline material [72][73][74]), which are in the range of 10 À21 -10 À27 cm 2 /s when extrapolated to 415°C. The non-surprising difference in iron diffusion coefficient between the different types of yttria stabilized zirconia is the difference between single crystalline material [72] and sintered powder [73,74], for which surface diffusion in the porosity and grain boundary diffusion can be expected. Due to the number of assumptions and the associated error, the diffusion coefficients calculated are a good estimate, confirmed by the comparison with Iltis et al [70], which can be also related to the very similar microstructure.…”

“…To be able to compare the diffusion coefficient provided by Iltis et al [70] and others [72][73][74], an estimate for the diffusion of the iron to the surface was made using the following procedure:…”

Atomic layer deposition of iron(III) oxide on zirconia nanoparticles in a fluidized bed reactor using ferrocene and oxygen

“…Iron oxide ALD has been demonstrated on a wide array of crystalline surfaces using Fe(thd) 3 and Fe(acac) 3 as precursors [28,29]. Recently, Fe (C 5 H 5 ) 2 (ferrocene) and oxygen have been used to deposit iron oxide films onto Si(100) and anodic aluminum [30].…”

Atomic Layer Deposition of Iron Oxide Thin Films and Nanotubes using Ferrocene and Oxygen as Precursors

“…A variety of different methods has been used to deposit iron oxide thin films, e.g., sputtering, [4] sol-gel, [5] aqueous chemical growth, [3] molecular beam epitaxy (MBE), [8] CVD, [9,10] and ALD. [11][12][13][14] There are also numerous reports of nanostructured iron oxide. [3,[15][16][17][18] Despite all reports of nanostructured materials, it is inherently difficult to fabricate arrays in a well-ordered pattern.…”