resumo
The solid solubilities of potential B-site dopants in LaNb1-xMxO4-delta, materials, M=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 <= 0.03). At the maximum value x=0.03, only compositions containing Ti, Ge, Ga and Si appeared pure at the limit of resolution of XRD. The literature phase diagram, La2O3-Nb2O5-ZrO2, has been re-analysed for compositions of low Zr-content around the composition LaNbO4. 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 LaNb0.98Ti0.02O4-delta was found to be much higher than that of an A-site, Sr-doped material, Sr0.02La0.98NbO4-delta, of similar acceptor dopant concentration. The Sr-doped composition offered higher conductivities than the Ti-doped composition up to approximately 900 degrees C. (C) 2011 Elsevier Inc. All rights reserved.
palavras-chave
DOPED LANBO4; FUEL-CELLS; CONDUCTIVITY; TRANSPORT; STABILITY; PRESSURE; SYSTEM; CA; SR
categoria
Chemistry
autores
Brandao, AD; Gracio, J; Mather, GC; Kharton, VV; Fagg, DP
nossos autores
Vladislav Kharton
Investigador Principal CovidadoGrupos
agradecimentos
This work was supported by the FCT, Portugal (Grants PTDC/CTM/64357/2006, FCT, SFRH/BD/60265/2009, FCT, PTDC/CTM/105424/2008, PTDC/CTM/100412/2008).