abstract
Phase composition, structural stability, electrical properties, thermochemical expansion and redox behavior of Pr-substituted SrTiO3 were assessed for potential application in solid oxide fuel cell anodes. XRD analysis confirms formation of single-phase perovskite-like Sr1-xPrxTiO3 +/-delta and Sr1-1.5xPrxTiO3 +/-delta (x = 0.02-0.30) ceramics under both oxidizing and reducing conditions, although microstructural studies indicate minor precipitation of TiO2 in reduced Sr-deficient ceramics with high Pr content. XPS analysis in combination with XRD suggests that Pr cations substitute into strontium sublattice in mixed 4+/3+ oxidation state and are essentially insoluble in titanium sublattice. Reduction at elevated temperatures results in 2-3 orders of magnitude increase of n-type electronic conductivity with respect to oxidized materials. Thermogravimetric and electrical studies demonstrate however very slow reduction kinetics at temperatures below 1273 K associated with nearly frozen equilibrium in cation sublattice and low oxygen vacancy concentration in oxidized materials. Electrical behavior is discussed in conjunction with defect chemistry of donor-doped strontium titanate. All oxidized and reduced materials exhibit moderate thermal expansion coefficients, compatible with that of common solid electrolytes, and a small contribution of chemical expansion on reduction. (C) 2013 Elsevier B.V. All rights reserved.
keywords
NB-DOPED SRTIO3; STRONTIUM-TITANATE; LOW-TEMPERATURES; SOFC ANODES; PRASEODYMIUM; DIFFUSION; CERAMICS; SYSTEM; DEFECT; GAS
subject category
Chemistry; Electrochemistry; Energy & Fuels; Materials Science
authors
Yaremchenko, AA; Patricio, SG; Frade, JR
our authors
Aleksey Yaremchenko
Principal Researcher
Jorge Ribeiro Frade
Retired Professor
Sónia Gonçalves Patrício
Assistant ResearcherGroups
G3 - Electrochemical Materials, Interfaces and Coatings
G5 - Biomimetic, Biological and Living Materials
Projects
ORIEL - Oriented Lanthanum Silicate Thin Film Electrolytes for IT-SOFCS (PTDC/CTM-CER/118933/2010)
acknowledgements
This work was supported by the FCT, Portugal (projects BPD/75943/2011, PTDC/CTM-CER/118933/2010 and PEst-C/CTM/LA0011/2011, and Ciencia program). Authors are grateful to Prof. Carlos Sa (CEMUP) for the helpful discussion of XPS results.