Solid‐state NMR study of dopant effects on the chemical properties of Mg‐, In‐, and Al‐doped SnP2O7 |
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Authors: | Masakazu Nishida Tomoko Tanaka Haruhiko Fukaya Wataru Kanematsu |
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Institution: | National Institute of Advanced Industrial Science and Technology (AIST), , Nagoya, 463‐8560 Japan |
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Abstract: | The effects of doped low‐valence cations on the properties of the SnP2O7 proton conductor at ambient temperature are investigated from changes in solid‐state NMR spectra and nuclear magnetic relaxation times. Although the T1H values increased with decreasing acidity as a result of cation exchange, the 1H chemical shifts moved to lower field in Al‐ and In‐doped materials compared with undoped ones. Furthermore, the shifts changed to higher field in Mg‐doped materials, suggesting the existence of different protonic species in those materials. The bulk phosphate chemical shifts in the 31P dipolar‐decoupling MAS NMR spectra were very similar, regardless of the nature and amount of the doping species. On the other hand, by 1H/31P cross‐polarization MAS NMR, P2O7 signals interacting with an interstitial proton Q1(proton)] were observed in all the undoped and doped SnP2O7, while acidic P–OH‐type phosphate signals Q1(acid)] were additionally observed in the Mg‐doped conductor. The different affinity of the proton with the dopants and phosphates caused lower conductivity and larger activation energy in the Mg‐doped materials, compared with those in the In‐ and Al‐doped materials. Copyright © 2014 John Wiley & Sons, Ltd. |
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Keywords: | NMR 31P 1H cross‐polarization relaxation time analysis proton conductor doping effect |
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