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Diffusion and correlation effects in iron-doped CoO

Journal of Physics and Chemistry of Solids
Publication Date
DOI: 10.1016/0022-3697(85)90036-8


Abstract The diffusion of 59Fe and 60Co has been measured in pure CoO and dilute iron-doped CoO, (Co 1− c Fe c O, as a function of temperature (1000–1400°C) and oxygen partial pressure P o 2), (10 −7 ≦ P o 2 ≦ 0 21 atm) The enhancement factors for the diffusivities of iron and cobalt are nearly identical, which suggests that the primary cause of the enhancement is the increased concentration of charge-compensating cation vacancies with the addition of iron. The Fe ions dissolved in CoO appear to exist as a mixture of Fe 2+ and Fe 3+ ions, the fraction of iron ions in the three-plus state decreases with decreasing P o 2 The simultaneous diffusion of 52Fe and 59Fe has been measured as a function of (itpo; at 1200°C The correlation factor for Fe impurity diffusion determined from the isotope-effect measurements is about the same as that for self-diffusion in CoO at high (itP o 2 (2 × 10 −3 ≦ p o 2 ≦ 0 21 atm), but increases slightly with decreasing p O 2 Both the enhancement-effect and isotope-effect experiments suggest that the nearestneighbor interactions between Fe ions and vacancies is small, and that the dissolved Fe ions do not have strongly bound electron holes.

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