The interactions of H and H 2 with W(1 0 0)-c(2 Â 2)Cu and W(1 0 0) have been investigated through density functional theory (DFT) calculations to elucidate the effect of Cu atoms on the reactivity of the alloy. Cu atoms do not alter the attraction towards top-W sites felt by H 2 molecules approachi
Effects of Fe-additions on sintering and transport properties of Yb2Ti2 − yFeyO7 − δ
✍ Scribed by A.L. Horovistiz; D.P. Fagg; J.C.C. Abrantes; J.R. Frade
- Publisher
- Elsevier Science
- Year
- 2007
- Tongue
- English
- Weight
- 318 KB
- Volume
- 27
- Category
- Article
- ISSN
- 0955-2219
No coin nor oath required. For personal study only.
✦ Synopsis
Partial substitution of Fe for Ti in Yb 2 Ti 2 -y Fe y O 7 -δ has been used to improve the sinterability of these ion conducting pyrochlore-type materials, and to adjust their transport properties. Fe additions displace the maximum shrinkage rate to lower temperatures and allow the preparation of dense materials at lower firing temperatures. Impedance spectroscopy was used to de-convolute the effects of Fe additions on the bulk and grain boundary conductivities. The bulk conductivity was enhanced for relatively low Fe additions (<5%) and its activation energy was lowered. The grain boundary conductivity was also enhanced. The dependence of total conductivity on oxygen partial pressure shows that this enhancement corresponds to ionic conductivity. The onset of n-type conductivity is displaced to more reducing conditions with Fe addition.
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