Graduate Thesis Or Dissertation

 

Monte Carlo simulation of oxygen mobility in cubic zirconia Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/2r36v2437

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  • The focus of this thesis is a study of the thermodynamics and the transport of oxygen in yttrium-doped cubic zirconia (Zr0₂). This material is representative of other ceramics with the same crystal structure (Y-Ce0₂ etc.). The Monte Carlo technique as developed by Metropolis et al. is used to calculate thermodynamical equilibrium properties. The same technique is used to study the transport properties of oxygen vacancies in the system, which is justified when the applied external field is weak. At low temperatures the vacancies are trapped in the vicinity of the yttria due to the attractive yttrium-vacancy potential. At high temperatures the positions of the vacancies are completely random. The transition temperature of the order to disorder "phase change" is modified by adding a repulsive vacancy-vacancy interaction. The energetically lowest trapsites are depopulated with increasing strength of the vacancy-vacancy repulsion. The transition temperature drops for a weak, but increases again for a strong repulsion. A similar behavior is found for the energy capacity of the system. The conduction of the system is described by an Arrhenius behavior. The activation energy is sensitive to the mutual repulsion of the vacancies. The activation energy for conduction exhibits a drop for weak repulsions. The dependence of the transition temperature and the energy capacity on the concentration show similar features. The activation energy also depends on the concentration, but the connection is not fully understood. The experimentally observed dramatic drop of the conductivity for highly doped samples of Zr0₂ and Ce0₂ is not reproduced, because it is due to an increase in the interstitial barrier height, which is not built into this model.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-06-10T16:58:23Z (GMT) No. of bitstreams: 1 GutekunstBernd1988.pdf: 509089 bytes, checksum: 83abd6b64ed70031937affe886488a0b (MD5)
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-07-16T22:53:36Z (GMT) No. of bitstreams: 1 GutekunstBernd1988.pdf: 509089 bytes, checksum: 83abd6b64ed70031937affe886488a0b (MD5)
  • description.provenance : Made available in DSpace on 2013-07-16T22:53:36Z (GMT). No. of bitstreams: 1 GutekunstBernd1988.pdf: 509089 bytes, checksum: 83abd6b64ed70031937affe886488a0b (MD5) Previous issue date: 1987-06-15

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