Oxygen diffusion in Bi2O3-doped ZnO

Sabioni, Antônio Claret Soares; Ferraz, Wilmar Barbosa; Pais, Rafael Witter Dias; Huntz, A.M.; Jomard, François

doi:10.1590/s1516-14392008000200019

Cited by 6 publications

(2 citation statements)

References 10 publications

(10 reference statements)

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“…The observed Zn concentration profiles strongly resemble the profiles reported by Sabioni et al for the diffusion of Zn in polycrystalline ceramics. , A typical concentration profile is shown in Figure . It shows the Zn content in a pellet that reacted for 90 min at 1000 °C, as measured by EPMA.…”

Section: Methodssupporting

confidence: 85%

Gas–Solid Reaction Kinetics of ZnFe₂O₄Formation from 907 to 1100 °C

et al. 2015

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The reaction kinetics of Zn vapor with Fe3O4 (magnetite) were studied from 907 to 1100 °C using a new experimental setup that only allows contact between the reactants through a gas-solid reaction. Hematite was used to create the reaction pellets. Because of the reducing atmosphere in the setup, a magnetite layer is formed on the outside of the pellet, which in turn reacts with the Zn vapor. After reaction, Zn concentration profiles were measured in the reacted magnetite layer using field-emission gun electron probe microanalysis. The reaction was confirmed to be diffusion-controlled. The effect of both volume and grain-boundary diffusion was observed in each experiment. The temperature dependence of both the volume and grain-boundary diffusion coefficients was obtained along with the activation energies of the diffusion coefficients. This study provides crucial information for the development of technologies that are dependent on the reaction. One example is the in-process separation technology for the separation of Zn vapor from electric arc furnace off-gas.

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Section: Methodssupporting

confidence: 85%

Gas–Solid Reaction Kinetics of ZnFe₂O₄Formation from 907 to 1100 °C

et al. 2015

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“…In order to explore the effect of the oxygen vacancy concentration on the dynamics, the annealing period was varied between 10 and 20 min, creating different oxygen vacancy (and hence donor) concentrations in the near-surface layers. [73][74][75] The sample was then allowed to cool in the presence of oxygen, before a low temperature anneal (603 K, 20 min), followed by a short high temperature anneal in vacuo (1023-1043 K, 10 min), 76 completing the cleaning process. A nal high temperature ash anneal in vacuo has previously been used to remove residual adsorbed oxygen; 76 here it was found to be necessary to eliminate charging during the pump-probe experiment.…”

Section: Zno Preparationmentioning

confidence: 99%

Dynamics in next-generation solar cells: time-resolved surface photovoltage measurements of quantum dots chemically linked to ZnO (101̄0)

et al. 2014

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The charge dynamics at the surface of the transparent conducting oxide and photoanode material ZnO are investigated in the presence and absence of light-harvesting colloidal quantum dots (QDs). The time-resolved change in surface potential upon photoexcitation has been measured in the m-plane ZnO (101[combining macron]0) using a laser pump-synchrotron X-ray probe methodology. By varying the oxygen annealing conditions, and hence the oxygen vacancy concentration of the sample, we find that dark carrier lifetimes at the ZnO surface vary from hundreds of μs to ms timescales, i.e. a persistent photoconductivity (PPC) is observed. The highly-controlled nature of our experiments under ultra-high vacuum (UHV), and the use of band-gap and sub-band-gap photoexcitation, allow us to demonstrate that defect states ca. 340 meV above the valence band edge are directly associated with the PPC, and that the PPC mediated by these defects dominates over the oxygen photodesorption mechanism. These observations are consistent with the hypothesis that ionized oxygen vacancy states are responsible for the PPC in ZnO. The effect of chemically linking two colloidal QD systems (type I PbS and type II CdS-ZnSe) to the surface has also been investigated. Upon deposition of the QDs onto the surface, the dark carrier lifetime and the surface photovoltage are reduced, suggesting a direct injection of charge carriers into the ZnO conduction band. The results are discussed in the context of the development of next-generation solar cells.

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