Effects of Fe-additions on sintering and transport properties of Yb2Ti2-yFeyO7-delta

authors	Horovistiz, AL; Fagg, DP; Abrantes, JCC; Frade, JR
nationality	International
journal	JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords	grain boundaries; electrical conductivity; impedance; ionic conductivity; pyrochlore
keywords	FUEL-CELL MATERIALS; IONIC-CONDUCTIVITY; PYROCHLORE; SYSTEM; TEMPERATURE; FLUORITE
abstract	Partial substitution of Fe for Ti in Yb2Ti2-yFeyO7-delta has been used to improve the sinterability of these ion conducting pyrochlore-type materials, and to adjust their transport properties. Fe additions displace the maximum shrinkage rate to lower temperatures and allow the preparation of dense materials at lower firing temperatures. Impedance spectroscopy was used to de-convolute the effects of Fe additions on the bulk and grain boundary conductivities. The bulk conductivity was enhanced for relatively low Fe additions (< 5%) and its activation energy was lowered. The grain boundary conductivity was also enhanced. The dependence of total conductivity on oxygen partial pressure shows that this enhancement corresponds to ionic conductivity. The onset of n-type conductivity is displaced to more reducing conditions with Fe addition. (c) 2007 Published by Elsevier Ltd.
publisher	ELSEVIER SCI LTD
issn	0955-2219
year published	2007
volume	27
issue	13-15
beginning page	4283
ending page	4286
digital object identifier (doi)	10.1016/j.jeurceramsoc.2007.02.133
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000248822800151