resumo
Mechanochemical preparation of Sr0.02La0.98Nb1-xVxO4-delta was demonstrated for values of x = 0 and 0.15. Crystallinity could be improved by calcining at 1073 K. On cooling, the high temperature scheelite phase was retained to room temperature. Several novel sintering additives for LaNbO4 materials have been tested. The most successful were Cu3Nb2O8 and CuV2O6, which reduced the temperature of maximum shrinkage rate to temperatures similar to 1173 K. The additive CuV2O8 was shown to increase densification and promote grain growth. A mechanosynthesised sample of Sr0.02La0.98Nb0.85V0.15O4-delta + 2 mol% CuV2O6 could be densified to similar to 90% that of the theoretical by hybrid microwave sintering at 1168 K for 5 min. The scheelite phase in this material was retained to room temperature, against the normal thermodynamic tendency. Impedance spectroscopy in wet and dry, nitrogen and oxygen atmospheres suggested that the bulk conductivity of this material is unaffected by the sintering aid, whereas the grain boundary conductivity was impaired and exhibited n-type conductivity behaviour, characteristic of the additive. The concentration of this promising additive should be reduced in further work. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
palavras-chave
FINITE PARTICLE-SIZE; CONTINUOUS TRANSFORMATION; SURFACE CONSTRAINT; SOLID-ELECTROLYTE; CERAMICS; LANBO4; LA0.995CA0.005NBO4; NIOBATE
categoria
Chemistry; Electrochemistry; Energy & Fuels
autores
Brandao, AD; Antunes, I; Frade, JR; Torre, J; Mikhalev, SM; Fagg, DP
nossos autores
Isabel Alexandra Gonçalves Antunes
Investigador Júnior
Jorge Ribeiro Frade
Professor(a) Jubilado(a)
José António Perez de la Torre
Bolseiro de pós-Doutoramento
Sergey Mikhalev
Bolseiro de pós-Doutoramentoagradecimentos
This work was supported by the FCT, Portugal (grants PTDC/CTM/64357/2006, SFRH/BD/60265/2009, PTDC/CTM/105424/2008, PTDC/CTM/100412/2008).