Microstructural effects on electrical conductivity relaxation in nanoscale ceria thin films

Journal Article · Thu May 07 00:00:00 EDT 2009 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3126092· OSTI ID:21559711

Tsuchiya, Masaru; Ramanathan, Shriram ^[1]; Bojarczuk, Nestor A; Guha, Supratik ^[2]

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1. Harvard School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)
2. IBM T. J. Watson Research Center, Yorktown Heights, New York 10514 (United States)

Microstructure evolution and electrical conductivity relaxation kinetics in highly textured and nanocrystalline dense ceria thin films ({approx}65 nm) are reported in this paper. Highly textured films were grown on sapphire c-plane substrates by molecular beam synthesis (MBS) with orientation relationship (111)CeO{sub 2}||(0001)Al{sub 2}O{sub 3} and [110]CeO{sub 2}||[1210]Al{sub 2}O{sub 3}. No significant structural changes were observed in highly textured films even after extensive annealing at high temperature. In contrast to MBS grown films, ceria films grown by electron beam evaporation at room temperature had polycrystalline structure with {approx}10 nm grains, which grew to {approx}30 nm upon annealing at 1173 K. Grain growth kinetics was self-limiting and the out-of-plane orientation was found to be substrate dependent. From conductivity relaxation measurements, oxygen exchange rate in highly textured thin films was found to be much slower than that in polycrystalline films. The response time for highly textured films to changes in P(O{sub 2}) from 1.07x10{sup -12} to 5.43x10{sup -10} Pa at 1148 K was 0.65 s, whereas that for polycrystalline films was 0.13 s under identical conditions. From temperature dependent experiments, activation energy for relaxation time was found to be similar, suggesting similar rate-limiting mechanisms in polycrystalline and highly textured films. The results highlight the importance of near-surface defects in controlling kinetics of oxygen incorporation into nanostructured oxides. In a broader context, the results maybe of relevance to designing catalytic surfaces in solid state ionic devices such as fuel cells.

• OSTI ID: 21559711
• Journal Information: Journal of Chemical Physics, Vol. 130, Issue 17; Other Information: DOI: 10.1063/1.3126092; (c) 2009 American Institute of Physics; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACTIVATION ENERGY
ALUMINIUM OXIDES
ANNEALING
CERIUM OXIDES
ELECTRIC CONDUCTIVITY
ELECTRON BEAMS
EVAPORATION
KINETICS
MICROSTRUCTURE
MOLECULAR BEAM EPITAXY
MOLECULAR BEAMS
NANOSTRUCTURES
OXYGEN
POLYCRYSTALS
RELAXATION
SAPPHIRE
SOLID OXIDE FUEL CELLS
SURFACES
TEMPERATURE RANGE 0400-1000 K
THIN FILMS
ALUMINIUM COMPOUNDS
BEAMS
CERIUM COMPOUNDS
CHALCOGENIDES
CORUNDUM
CRYSTAL GROWTH METHODS
CRYSTALS
DIRECT ENERGY CONVERTERS
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELEMENTS
ENERGY
EPITAXY
FILMS
FUEL CELLS
HEAT TREATMENTS
HIGH-TEMPERATURE FUEL CELLS
LEPTON BEAMS
MINERALS
NONMETALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARTICLE BEAMS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SOLID ELECTROLYTE FUEL CELLS
TEMPERATURE RANGE