Mechanochemical preparation, sintering aids and hybrid microwave sintering in the proton conductor Sr0.02La0.98Nb1-xVxO4-delta, x=0, 0.15
authors Brandao, AD; Antunes, I; Frade, JR; Torre, J; Mikhalev, SM; Fagg, DP
nationality International
journal INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
author keywords LaNbO4; Proton conductor; Hybrid microwave sintering; Mechanochemical reaction; Sintering aids; Scheelite/Fergusonite
keywords FINITE PARTICLE-SIZE; CONTINUOUS TRANSFORMATION; SURFACE CONSTRAINT; SOLID-ELECTROLYTE; CERAMICS; LANBO4; LA0.995CA0.005NBO4; NIOBATE
abstract 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.
publisher PERGAMON-ELSEVIER SCIENCE LTD
issn 0360-3199
year published 2012
volume 37
issue 8
beginning page 7252
ending page 7261
digital object identifier (doi) 10.1016/j.ijhydene.2011.12.041
web of science category Chemistry, Physical; Electrochemistry; Energy & Fuels
subject category Chemistry; Electrochemistry; Energy & Fuels
unique article identifier WOS:000303952300099
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