Surface oxidation kinetics of Si3N4-4%Y2O3 powders studied by Bremsstrahlung-excited Auger spectroscopy |
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Authors: | Pu Sen Wang S M Hsu S G Malghan T N Wittberg |
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Affiliation: | (1) Ceramics Division, National Institute of Standards and Technology, 20899 Gaithersburg, MD, USA;(2) University of Dayton Research Institute, 45469 Dayton, OH, USA |
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Abstract: | Samples of silicon nitride powder containing 4.0% Y2O3 in weight were heated in air at temperatures between 900 and 1000 °C. The average SiO2 layer thickness on the Si3N4 powder particles, as a function of time at a particular temperature, was measured by Bremsstrahlung-excited Auger electron spectroscopy. Oxidation was found to follow a linear rate law with an activation energy of 56±1.5 kcal mol–1. The yttrium level measured by X-ray photoelectron spectroscopy was also found to decrease as a function of the oxide layer thickness. This suggests that there is a reaction between the Si3N4 and Y2O3 particles which results in the formation of an yttrium-rich phase at the interface between the surface SiO2 layer and the underlying Si3N4 particle. |
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