Abstract: This paper presents results of research aimed at development of efficient synthesis procedures and characterization of oxide-ion conducting electrolytes based on doped lanthanum silicate with the apatite structure promising for design of solid oxide fuel cells operating at intermediate temperatures. Phase-pure nanocrystalline powders of doped lanthanum silicate La10-y(Sr, Mg)ySi6-x(Fe, Al)xO26+z were successfully prepared via the mechanical activation of a mixture of solid reagents in high-power planetary ball mills followed by annealing at 700-1000o C provided reagents nature and activation parameters are properly optimized. Real/defect structure and surface properties of these materials as a function of both composition, preparation route and sintering temperature were studied by combination of TEM with EDX, XRD, EXAFS, Mossbauer spectroscopy (for Fe-doped samples), Si and Al MAS NMR (for Al-doped samples), UV-Vis, XPS and SIMS methods. Redistribution of Me3+ dopants between tetrahedral and octahedral positions (including those in the perovskite-like microinclusions) and condensation of SiO4 tetrahedra was revealed and analyzed. Effects of samples chemical composition and real structure on their transport properties characterized by the oxygen isotope heteroexchange for powders and impedance spectroscopy for dense materials were analyzed. For best compositions, intermediate temperature conductivity is close to that of Gd-doped ceria. Isotope exchange data support a model in which the oxygen mobility is determined by the non-linear cooperative movement of oxide ions between interstitial and tetrahedral positions. Approaches to design of cathode and anode materials for solid oxide fuel cells with the apatite-type electrolyte compatible by thermal expansion and chemical tolerance were elaborated. For cathodes, nanocomposites comprised of complex Ni-containing perovskites and Fe-doped La silicate were found to be promising materials due to chemical compatibility and non-additive increase of both reactivity in O2 activation and oxygen mobility due to positive role of interfaces and moderate redistribution of elements between domains of different phases. For anode materials operating in the mode of internal steam reforming of methane, the highest activity and coking stability were demonstrated by nanocomposites comprised of Ni, Sr-doped apatite and Sr-doped La titanate. Button-size cells were manufactured using both traditional and advanced (spark plasma) sintering techniques. Half cells consisting of electrolyte and anode were made by means of SPS and cathodes were applied afterwards by means of electrophoretic deposition. Polarization characteristics of cathode materials were obtained and analyzed with a due regard for their composition and microstructure.

Cite: Sadykov V. , Kharlamova T. , Pavlova S. , Muzykantov V. , Ishchenko A. , Krieger T. , Lapina O. , Uvarov N. , Chaikina M. , Pavlyukhin Y. , Argirusis C. , Sourkouni G. , Szepanski C. , Bebelis S. , Gasparyan H. , Stathopoulos V. , Jothinathan E. , Van der Biest O.
Doped Lanthanum Silicates with the Apatite Structure as Oxide-Ion Conducting Electrolytes: Synthesis, Characterization and Application for Design of Intermediate Temperature Solid Oxide Fuel Cell.
Monography chapter Lanthanum: Compounds, Production and Applications. – Nova Science Publishers, Inc.., 2011. – C.1-108. – ISBN 9781617281112. Scopus РИНЦ ANCAN

Dates:

Published print:

Jan 1, 2011

Identifiers:

Scopus:	2-s2.0-84892956470
Elibrary:	21881310
Chemical Abstracts:	2011:280784
Chemical Abstracts (print):	155:332303

Citing:

DB	Citing
Scopus	4
Elibrary	2