Microstructure Evolution and Cation Interdiffusion in Thin Sm₂O₃ Films on CeO₂ Substrates

Abstract

Samaria (Sm 2 O 3 ) thin films with a thickness of 180 nm were deposited on polycrystalline CeO 2 substrates by pulsed layer deposition to study phase formation and bulk cation interdiffusion in the Ce 1x Sm x O 2x/2 system after annealing at temperatures between 987°C and 1266°C. Transmission electron microscopy combined with electron diffraction and analytical techniques was applied for phase determination. The cubic fluorite and cubic bixbyite phases were observed at low and intermediate Sm concentrations. The monoclinic phase occurs only at very high Sm concentrations due to the low Ce-solubility in Sm 2 O 3 . Furthermore, a cubic phase with I2 1 3 structure was observed at higher Sm concentrations. Cation interdiffusion coefficients were derived from Sm concentration profiles across the Sm 2 O 3 /CeO 2 interface using the diffusion-couple solution of the diffusion equation. The temperature dependence of interdiffusion coefficients is well described by an Arrhenius-type relation, which yields an activation enthalpy of 2.26 eV/atom for bulk cation interdiffusion.H. Chan-contributing editor Manuscript No. 34455.

Design and fabrication of mesoporous heterogeneous basic catalysts

“…Ceria-based materials have found applications in a wide range of fields, such as catalysis, [276][277][278][279][280] adsorption, 281 fuel cells, [282][283][284] and sensing. Among the rare earth family, Ce is the most abundant element.…”

“…Cerium is even more abundant in the Earth's crust (66.5 ppm) than that of Cu (60.0 ppm). Ceria-based materials have found applications in a wide range of fields, such as catalysis, [276][277][278][279][280] adsorption, 281 fuel cells, [282][283][284] and sensing. [285][286][287] It is known that CeO 2 has a fluorite crystal structure, which is similar to that of ZrO 2 (slightly distorted fluorite structure).…”

Beneficial Lattice Strain in Heterogeneously Doped Ceria

“…This concern, however, would be highly unlikely to become an issue in this work because of the extremely low diffusion coefficients of cations in ceria at temperatures of 650 °C and below. Rochenhaüser et al investigated the cation interdiffusion between thin Gd 2 O 3 films on CeO 2 substrates 33. On the basis of that work, the Gd cation diffusion coefficient in CeO 2 can be estimated at about 2.8 × 10 −27 m 2 /s at 650 °C.…”