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Characteristics of La 0.85 Sr 0.15 MnO 3–δ Powders Synthesized by a Glycine‐Nitrate Process
Author(s) -
Peng R.,
Fan X.,
Jiang Z.,
Xia C.
Publication year - 2006
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.200600009
Subject(s) - materials science , stoichiometry , oxide , electrochemistry , samarium , conductivity , charge transfer coefficient , analytical chemistry (journal) , electrode , dielectric spectroscopy , polarization (electrochemistry) , activation energy , chemical engineering , inorganic chemistry , chemistry , cyclic voltammetry , chromatography , engineering , metallurgy
The amount of glycine added, i.e., the glycine/oxide molar ratio, k , is optimized for synthesizing La 0.85 Sr 0.15 MnO 3‐δ (LSM) powders by a glycine‐nitrate process. The specific surface area of the resultant LSM powders increases with this ratio, which indicates the deviation of the required glycine from the stoichiometric reaction. The powder is further characterized as a precursor for LSM‐SDC (samarium‐doped ceria) composite electrodes for solid oxide fuel cells. The electronic conductivity of the LSM‐SDC composite increases with increases in the glycine/oxide ratio. In addition, the ratio has an effect on the interfacial polarization resistance of the LSM‐SDC electrodes, as determined with symmetric cells using AC impedance spectroscopy. The lowest resistance is achieved using a LSM powder prepared with 20% more glycine than the stoichiometric requirement ( k = 1.2). The activation energies for electrochemical oxygen reduction are about 1.3 eV, when the ratio is below 1.2, and about 1.0 eV, when it exceeds 1.2. The activation energy suggests that oxygen ion transfer is the rate determining process for the LSM‐SDC electrode when k ≥ 1.2, whereas both mass transfer and charge transfer are the rate limiting steps when k < 1.2.