Содержание
- 2. Crystalline solids have a very regular atomic structure: that is, the local positions of atoms with
- 3. Point Defects Point defects in ionic solids I Frenkel defect: anion vacancy-interstitial cation pair. Schottky defect:
- 4. F-center: anion vacancy with excess electron replacing the missing anion e- M-center: two anion vacancies with
- 5. M corresonds to the species. These include: atoms - e.g. Si, Ni, O, Cl, vacancies -
- 6. Point Defects Kröger-Vink notation II = an aluminium ion sitting on an aluminium lattice site, with
- 7. Reaction involving defects must be: Example: Point Defects Defect chemical reaction Formation of a Schottky defect
- 8. Gperf: free energy of the perfect crystal hdef: enthalpy of formation of one defect sdvib: vibrational
- 9. Yanagida et al.: p. 60-61 Number of ways to arrange nv vacancies within a crystal with
- 10. Entropy Configurational Entropy Entropy originating from the many possibilities of arranging many vacancies Formation ("vibrational") Entropy
- 11. G n G0 Δhf G neq -TΔSc Gmin T=const. The stippled lines are for a higher
- 12. Point Defects Equilibrium Schottky defect concentration - Number of Schottky pairs: - Formation of a Schottky
- 13. Extrinsic defect concentration I - Total number of cation vacancies: - Substitution of a divalent cation
- 14. Point Defects ln(XV) 103/T XCa=10-4 10-5 10-6 10-4 10-5 10-6 cation vacancies anion vacancies - Temperature
- 15. Point Defects Nonstoichiometric defects In nonstoichiometric defect reactions the composition of the cystal changes as a
- 16. Atomic diffusion is a process whereby the random thermally-activated hopping of atoms in a solid results
- 17. Diffusion Type of diffusion Diffusion paths: HRTEM image of an interface between an aluminum (left) and
- 18. Types of diffusion kinetics: 3 regimes A, B and C are usually distinguished. They are represented
- 19. Diffusion Atomistic diffusion mechanisms Exchange mechanism Ring rotation mechanicsm Vacancy mechanism Interstitial mechanism Diffusion couple t0
- 20. Diffusion Fick’s 1. law dC dx C x The flux J in direction x of the
- 21. Diffusion Fick’s 2. law In regions where the concentration gradient is convex, the flux (and the
- 22. Diffusion Solutions to Fick’s 2. law I -Finite thin film source, one-dimensional diffusion into semi-infinite solid:
- 23. Diffusion 1-D diffusion 1-D diffusion from a finite point source
- 24. -Finite thin film source of constant concentration, one- dimensional diffusion into semi-infinite solid: c(x≠0,t=0): 0 c(x=0,t):
- 25. Diffusion Diffusion couple c(x c(x > 0,t=0): c2 +x -x c t1 t0 t0 c1 c2
- 26. Diffusion 1-D diffusion couple Diffusion profiles for 1-D diffusion couple for different diffusion times
- 27. Diffusion
- 28. - Distance x’ from a source with finite concentration where a certain small amount of the
- 29. Diffusion Diffusion: A thermally activated process I Energy of red atom= ER Minimum energy for jump
- 30. Diffusion Diffusion: A thermally activated process II The preexponential factor and the activation energy for a
- 31. Tracer diffusion coefficients of 18O determined by SIMS profiling for various micro- and nanocrystalline oxides: coarse
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