Electron Microscopical Investigation of Interdiffusion and by Christian Rockenhäuser

By Christian Rockenhäuser

Christian Rockenhäuser adresses section formation and cation interdiffusion of the GdxCe1-xO2-x/2-and SmxCe1-xO2-x/2-material structures at temperatures starting from 970 to 1270°C. Diffusion with CeO2/Sm2O3 and CeO2/Gd2O3 interfaces have been fabricated for the investigations. The ensuing response stages have been investigated using transmission electron microscopy (TEM) and make allowance conclusions in regards to the part diagrams within the tested temperature diversity. A miscibility hole will be governed out for GdxCe1-xO2-x/2 around the complete composition variety. Cation interdiffusion coefficients have been decided for either fabric structures through measuring and comparing focus profiles on the fabric interfaces. The activation enthalpies for interdiffusion have been calculated utilizing the temperature dependence of the interdiffusion coefficients. The learn for the 1st time compiles comprehensively the former effects concerning the section diagrams of the 2 fabric structures considering 1923.

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Additional resources for Electron Microscopical Investigation of Interdiffusion and Phase Formation at Gd2O3/CeO2- and Sm2O3/CeO2-Interfaces

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The fluorite→bixbyite phase transition was confirmed by Mandal et al. [114] in the Sm-concentration range between 40 at% and 50 at%. The cubic bixbyite phase was not validated for high Sm-concentrations, though. A biphasic phase field consisting of bibyite and monoclinic phases is suggested at about 95 at%. A study by Bevan et al. [104] predicts miscibility gaps between the fluorite and bixbyite phases and the bixbyite and monoclinic phases. Later measurements gave evidence for two miscibility gaps at 1600 ◦ C [115].

The effect of reaction-controlled RL formation is illustrated in the following. Here a layer of Smη Ce1-η O2-η/2 with bixbyite structure and thickness xbix growing between two saturated phases is considered as an example. The monoclinic Smζ Ce1-ζ O2-ζ/2 and Smθ Ce1-θ O2-θ/2 with fluorite structure have the saturation eq eq concentrations Cζ(mon) and Cθ(f lu) . The interface positions to the bixbyite layer are marked by xmb and xbf . The subscripts ζ > η > θ describe the composition of the compounds.

The second process is the rearrangement of atoms at the interfaces required for the growth of the compound layer. This may involve a reaction barrier. The effect of reaction-controlled RL formation is illustrated in the following. Here a layer of Smη Ce1-η O2-η/2 with bixbyite structure and thickness xbix growing between two saturated phases is considered as an example. The monoclinic Smζ Ce1-ζ O2-ζ/2 and Smθ Ce1-θ O2-θ/2 with fluorite structure have the saturation eq eq concentrations Cζ(mon) and Cθ(f lu) .

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