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Title: Nonlinear Impedance Analysis of La 0.4Sr 0.6Co 0.2Fe 0.8O 3-δ Thin Film Oxygen Electrodes

Abstract

Here, linear and nonlinear electrochemical impedance spectroscopy (EIS, NLEIS) were used to study 20 nm thin film La 0.6Sr 0.4Co 0.2Fe 0.8O 3-δ (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 themore » surface thermodynamics over exposure time.« less

Authors:
 [1];  [2];  [2];  [1]
  1. Univ. of Washington, Seattle, WA (United States). Dept. of Chemical Engineering
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Mechanical Engineering
Publication Date:
Research Org.:
Univ. of Washington, Seattle, WA (United States); National Energy Technology Laboratory (NETL), Pittsburgh, PA, Morgantown, WV (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division; USDOE Office of Fossil Energy (FE); Tohoku Univ., Sendai (Japan)
OSTI Identifier:
1438528
Grant/Contract Number:  
FE0009435; CNMS2013-292
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 163; Journal Issue: 9; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; impedance spectroscopy; perovskite; SOEC; SOFC; thin film

Citation Formats

Geary, Tim C., Lee, Dongkyu, Shao-Horn, Yang, and Adler, Stuart B. Nonlinear Impedance Analysis of La0.4Sr0.6Co0.2Fe0.8O3-δ Thin Film Oxygen Electrodes. United States: N. p., 2016. Web. doi:10.1149/2.0851609jes.
Geary, Tim C., Lee, Dongkyu, Shao-Horn, Yang, & Adler, Stuart B. Nonlinear Impedance Analysis of La0.4Sr0.6Co0.2Fe0.8O3-δ Thin Film Oxygen Electrodes. United States. doi:10.1149/2.0851609jes.
Geary, Tim C., Lee, Dongkyu, Shao-Horn, Yang, and Adler, Stuart B. Sat . "Nonlinear Impedance Analysis of La0.4Sr0.6Co0.2Fe0.8O3-δ Thin Film Oxygen Electrodes". United States. doi:10.1149/2.0851609jes. https://www.osti.gov/servlets/purl/1438528.
@article{osti_1438528,
title = {Nonlinear Impedance Analysis of La0.4Sr0.6Co0.2Fe0.8O3-δ Thin Film Oxygen Electrodes},
author = {Geary, Tim C. and Lee, Dongkyu and Shao-Horn, Yang and Adler, Stuart B.},
abstractNote = {Here, linear and nonlinear electrochemical impedance spectroscopy (EIS, NLEIS) were used to study 20 nm thin film La0.6Sr0.4Co0.2Fe0.8O3-δ (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.},
doi = {10.1149/2.0851609jes},
journal = {Journal of the Electrochemical Society},
issn = {0013-4651},
number = 9,
volume = 163,
place = {United States},
year = {2016},
month = {7}
}

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