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|a Geary, Tim C.
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|a Massachusetts Institute of Technology. Department of Materials Science and Engineering
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|a Lee, Dongkyu
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|a Shao-Horn, Yang
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|a Lee, Dongkyu
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|a Shao-Horn, Yang
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|a Adler, Stuart B.
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|a Nonlinear Impedance Analysis of La[subscript 0.4]Sr[subscript 0.6]Co[subscript 0.2]Fe[subscript0.8]O[subscript3-[subscript[delta]] Thin film Oxygen Electrodes
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|b Electrochemical Society,
|c 2017-03-28T13:58:43Z.
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|z Get fulltext
|u http://hdl.handle.net/1721.1/107745
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|a Linear and nonlinear electrochemical impedance spectroscopy (EIS, NLEIS) were used to study 20 nm thin film La[subscript 0.6]Sr[subscript 0.4]Co[subscript 0.2]Fe[subscript 0.8]O[subscript 3][subscript -][delta] (LSCF-6428) electrodes at 600°C in oxygen environments. LSCF films were epitaxially deposited on single crystal yttria-stabilized zirconia (YSZ) with a 5 nm gadolinium-doped ceria (GDC) protective interlayer. Impedance measurements reveal an oxygen storage capacity similar to independent thermogravimetry measurements on semi-porous pellets. However, the impedance data fail to obey a homogeneous semiconductor point-defect model. Two consistent scenarios were considered: a homogeneous film with non-ideal thermodynamics (constrained by thermogravimetry measurements), or an inhomogeneous film (constrained by a semiconductor point-defect model with a Sr maldistribution). The latter interpretation suggests that gradients in Sr composition would have to extend beyond the space-charge region of the gas-electrode interface. While there is growing evidence supporting an equilibrium Sr segregation at the LSCF surface monolayer, a long-range, non-equilibrium Sr stratification caused by electrode processing conditions offers a possible explanation for the large volume of highly reducible LSCF. Additionally, all thin films exhibited fluctuations in both linear and nonlinear impedance over the hundred-hour measurement period. This behavior is inconsistent with changes solely in the surface rate coefficient and possibly caused by variations in the surface thermodynamics over exposure time.
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|a National Energy Technology Laboratory (U.S.) Solid State Energy Conversion Alliance (SECA) Core Technology Program (Award Number DEFE0009435)
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|a United States. Dept. of Energy. Office of Basic Energy Science. Scientific User Facilities Division (grant CNMS2013-292)
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|a en_US
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|a Article
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|t Journal of The Electrochemical Society
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