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The tracer diffusion coefficient for niobium in rutile Ti[O.sub.2] single crystals which could be applied to the processing of Nb-doped Ti[O.sub.2]-based semiconductors using solid-state reactions between [Nb.sub.2][O.sub.5] and Ti[O.sub.2] is reported.

This work reports the effect of oxygen activity on surface segregation for TiO2 co-doped with two cations, indium and niobium (0.076 at.% In + 0.103 at.% Nb). In this work, we studied the effect of annealing at 1273 K in the gas phase of controlled oxygen activity on surface segregation of both ions. The applied oxygen activity included pure oxygen, p(O2) = 100 kPa, and argon, p(O2) = 10 Pa. The segregation-induced concentration gradients were determined using both secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The obtained results indicate that annealing of the studied TiO2 specimens in argon results in cooperative segregation of both ions leading to the formation of a surface structure involving comparative concentrations of both cations. However, annealing in oxygen results in preferential segregation of indium leading to the formation of a In2TiO5-type surface structure. The obtained results are considered in terms of the effect of multicomponent segregation on processing of the surface layer with controlled properties that are desired for specific applications. The present work indicates that oxygen activity may be used as the parameter in surface engineering of the solid solution. [ABSTRACT FROM AUTHOR]

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 In2 TiO5 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: [ABSTRACT FROM AUTHOR]

Exposure to particulate matter results in adverse health outcomes, especially in sensitive members of the community. Many communities that co-exist with industry are concerned about the perceived impact of emissions from that industry on their health. Such concerns have resulted in two studies in the Hunter Valley of New South Wales, Australia. The chemical composition of samples of particulate matter, collected over two 12-month sampling periods (2012 and 2014–2015) at six sites in the Hunter Valley and across two size fractions (PM2.5 and PM2.5–10) were input to a receptor model to determine the source of particulate matter influencing particle composition at the sites. Fourteen factors were found to contribute to particle mass. Of these, three source profiles common to all sites, size fractions, and sampling periods were sea salt, industry-aged sea salt and soil. Four source profiles were common across all sites for PM2.5 including secondary sulphate, secondary nitrate, mixed industry/vehicles, and woodsmoke. One source profile (other biomass smoke) was only identified in PM2.5 at Singleton and Muswellbrook, two source profiles (mixed industry/shipping and vehicles) were only identified in PM2.5 at Newcastle, Beresfield, Mayfield, and Stockton, and one source (primary nitrate) was only identified at Stockton in PM2.5. Three sources (bioaerosol, light absorbing particles (coal dust), and industry) were only identified in the PM2.5–10 size fraction at Mayfield and Stockton. The contribution of the soil factor to PM2.5 mass was consistent across the sites, while the fresh sea salt factor decreased with distance from the coast from 23% at Stockton to 3% at Muswellbrook, and smoke increased with distance from the coast. Primary industry was greatest at Stockton (due to the influence of ammonium nitrate emitted from a prilling tower) and lowest inland at Muswellbrook. In general, primary emissions across the sites accounted for 30% of the industry sources. The largest contribution to PM2.5 was from secondary sources at all sites except at Muswellbrook, where woodsmoke and industry sources each made an equal contribution of 40%. In general, secondary reactions accounted for approximately 70% of the industry source, although at Stockton, with the presence of the prilling tower, this split was 50% primary and 50% secondary and at Muswellbrook, the split was 20% primary and 80% secondary. These findings add to the evidence base required to inform policies and programs that will improve air quality in the Hunter Valley. [ABSTRACT FROM AUTHOR]

Metal oxide pseudocapacitors are limited by low electrical and ionic conductivities. The present work integrates defect engineering and architectural design to exhibit, for the first time, intercalation pseudocapacitance in CeO 2- x . An engineered chronoamperometric electrochemical deposition is used to synthesize 2D CeO 2- x nanoflakes as thin as ∼12 nm. Through simultaneous regulation of intrinsic and extrinsic defect concentrations, charge transfer and charge-discharge kinetics with redox and intercalation capacitances together are optimized, where reduction increases the gravimetric capacitance by 77% to 583 F g -1 , exceeding the theoretical capacitance (562 F g -1 ). Mo ion implantation and reduction processes increase the specific capacitance by 133%, while the capacitance retention increases from 89 to 95%. The role of ion-implanted Mo 6+ is critical through its interstitial solid solubility, which is not to alter the energy band diagram but to facilitate the generation of electrons and to establish the midgap states for color centers, which facilitate electron transfer across the band gap, thus enhancing n-type semiconductivity. Critically, density functional theory simulations reveal, for the first time, that the reduction causes the formation of ordered oxygen vacancies that provide an atomic channel for ion intercalation. These channels enable intercalation pseudocapacitance but also increase electrical and ionic conductivities. In addition, the associated increased active site density enhances the redox such that the 10% of the Ce 3+ available for redox (surface only) increases to 35% by oxygen vacancy channels. These findings are critical for any oxide system used for energy storage systems, as they offer both architectural design and structural engineering of materials to maximize the capacitance performance by achieving accumulative surface redox and intercalation-based redox reactions during the charge/discharge process.