B-site substitutions in LaNb1−xMxO4−δ materials in the search for potential proton conductors (M=Ga, Ge, Si, B, Ti, Zr, P, Al)
✍ Scribed by A.D. Brandão; J. Gracio; G.C. Mather; V.V. Kharton; D.P. Fagg
- Book ID
- 104030803
- Publisher
- Elsevier Science
- Year
- 2011
- Tongue
- English
- Weight
- 746 KB
- Volume
- 184
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The solid solubilities of potential B-site dopants in LaNb 1-x M x O 4 À d , materials, M¼ Ga, Ge, Si, Al, B, P, Zr or Ti, have been investigated in the search for possible novel proton conductors. In general, the solubility levels of these cations were found to be very low (x r0.03). At the maximum value x ¼ 0.03, only compositions containing Ti, Ge, Ga and Si appeared pure at the limit of resolution of XRD. The literature phase diagram, La 2 O 3 -Nb 2 O 5 -ZrO 2 , has been re-analysed for compositions of low Zr-content around the composition LaNbO 4 . The electrical properties of phase pure Ti-doped compositions have been studied. Higher bulk and total conductivities were observed in wet than dry conditions, suggesting a significant protonic contribution to total conductivity. In wet conditions, the activation energy for bulk conductivity of LaNb 0.98 Ti 0.02 O 4-d was found to be much higher than that of an A-site, Sr-doped material, Sr 0.02 La 0.98 NbO 4-d , of similar acceptor dopant concentration. The Sr-doped composition offered higher conductivities than the Ti-doped composition up to approximately 9001C.