“…The equilibration kinetics, which is related to the diffusion of lattice species in the chemical potential gradient (chemical diffusion), may be monitored using defect-related properties, such as electrical conductivity. The kinetics data may then be used for the determination of the chemical diffusion coefficient. − The interpretation of kinetics is simple when only one type of defect takes part in equilibration. However, when several defects with different diffusion rates take part in overall mass transport, then the equilibration kinetics is more complex.…”
Section: Defect-related Propertiesmentioning
confidence: 99%
“…Bulk oxidation of rutile at elevated temperatures can be considered in terms of two oxidation stages: , First stage: fast oxygen incorporation leading to the gas/solid equilibrium with respect to fast ionic defects, oxygen vacancies, and titanium interstitials. Second stage: slow propagation of the equilibrium concentration of titanium vacancies. 30 Schematic representation of the work function changes of TiO 2 during oxidation and reduction in the absence and presence of hydrogen (top and bottom, respectively) …”
“…The equilibration kinetics, which is related to the diffusion of lattice species in the chemical potential gradient (chemical diffusion), may be monitored using defect-related properties, such as electrical conductivity. The kinetics data may then be used for the determination of the chemical diffusion coefficient. − The interpretation of kinetics is simple when only one type of defect takes part in equilibration. However, when several defects with different diffusion rates take part in overall mass transport, then the equilibration kinetics is more complex.…”
Section: Defect-related Propertiesmentioning
confidence: 99%
“…Bulk oxidation of rutile at elevated temperatures can be considered in terms of two oxidation stages: , First stage: fast oxygen incorporation leading to the gas/solid equilibrium with respect to fast ionic defects, oxygen vacancies, and titanium interstitials. Second stage: slow propagation of the equilibrium concentration of titanium vacancies. 30 Schematic representation of the work function changes of TiO 2 during oxidation and reduction in the absence and presence of hydrogen (top and bottom, respectively) …”
“…Surface potential is mainly developed by surface ionization on the metal oxide surface and adsorption of ions from the electrolyte on the particle surface. When metal oxide nanoparticles are dispersed in water, because of the reactivity of the defective surface structure, the OH À ion is attached to the oxygen vacancies present in the crystal structure, and the H þ ion is attached to the lattice O À ion to form OH À ion on the metal oxide surface (Nowotny et al, 2006). Apart from the potential determining ions (PDI) present in the solutions (H þ , OH À in metal oxides), the concentration and type of electrolyte also affects the potential developed at the particle surface and the agglomeration size (Jiang et al, 2009;Suttiponparnit et al, 2011).…”
“…Oxidation or reduction of TiO 2 results in a change in nonstoichiometry and the related Fermi level. However, imposition of well‐defined oxygen activity requires knowledge of the chemical diffusion coefficient …”
This work determines the self‐diffusion coefficients of indium in TiO2 single crystal (rutile). Diffusion concentration profiles were imposed by deposition of a thin surface layer of InCl3 on the TiO2 single crystal and subsequent annealing in the temperature range 1073–1573 K. The diffusion‐induced concentration profiles of indium as a function of depth were determined using secondary ion mass spectrometry (SIMS). These diffusion profiles were used to calculate the self‐diffusion coefficients of indium in the polycrystalline In2TiO5 surface layer and the TiO2 single crystal. The temperature dependence of the respective diffusion coefficients, in the range 1073–1573 K, can be expressed by the following formulas: DIn−In2TiO5=1.9×10−13exp(−1420.35emkJ/molRT)[m2s−1] and DIn−TiO2=7.4×10−4exp(−3160.35emkJ/molRT)[m2s−1] The obtained activation energy for bulk diffusion of indium in rutile (316 kJ/mol) is similar to that of zirconium in rutile (325 kJ/mol). The determined diffusion data can be used in selection of optimal processing conditions for TiO2–In2O3 solid solutions.
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