Understanding Chemical Expansion in Non-Stoichiometric Oxides: Ceria and Zirconia Case Studies
نویسنده
چکیده
Atomic scale computer simulations, validated with experimental data, are used to uncover the factors responsible for defect-induced chemical expansion observed in non-stoichiometric oxides, exemplifi ed by CeO 2 and ZrO 2 . It is found that chemical expansion is the result of two competing processes: the formation of a vacancy (leading to a lattice contraction primarily due to electrostatic interactions) and the cation radius change (leading to a lattice expansion primarily due to steric effects). The chemical expansion coeffi cient is modeled as the summation of two terms that are proportional to the cation and oxygen radius change. This model introduces an empirical parameter, the vacancy radius, which can be reliably predicted from computer simulations, as well as from experimental data. This model is used to predict material compositions that minimize chemical expansion in fl uorite structured solid oxide fuel cell electrolyte materials under typical operating conditions.
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تاریخ انتشار 2012