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Title: SrZrO 3 Formation at the Interlayer/Electrolyte Interface during (La 1-xSr x) 1-δCo 1-yFe yO 3 Cathode Sintering

Abstract

This work probes the formation of SrZrO 3 at the SDC/YSZ interface (Sm doped ceria, SDC; Y stabilized zirconia, YSZ) during (La 1-xSr x) 1-δCo1 -yFe yO 3 (LSCF) cathode sintering. SEM/EDS and grazing incidence X-ray diffraction results of annealed LSCF and YSZ samples reveal that even without physical contact between LSCF and YSZ, SrZrO 3 was formed on the surface of YSZ, preferentially at the grain boundaries. It was suspected that the SrZrO 3 formation is due to the Sr-containing gas species diffused through the pores of the SDC layer and reacted with the YSZ electrolyte. Computational thermodynamics was adopted to predict the gas species formed in air during sintering by using the La-Sr-Co-Fe-O-H thermodynamic database. Sr(OH) 2 is identified as the dominant Sr-containing gas species under the experimental conditions. In addition, it was found that A-site deficiency in LSCF could effectively suppress the SrZrO 3 formation while a dense and pore-free SDC interlayer is required to totally block the SrZrO 3 formation. As a result, cell performance was significantly improved for a cell with a dense SDC interlayer fabricated by pulsed laser deposition, due to elimination of SrZrO 3 formation and therefore reduced interfacial resistance.

Authors:
 [1];  [2];  [1];  [1];  [1];  [3]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  2. Florida International Univ., Miami, FL (United States)
  3. Florida International Univ., Miami, FL (United States); Worcester Polytechnic Institute, Worcester, MA (United States)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1390433
Report Number(s):
PNNL-SA-127510
Journal ID: ISSN 0013-4651; AA6040000
Grant/Contract Number:
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of the Electrochemical Society
Additional Journal Information:
Journal Volume: 164; Journal Issue: 10; Journal ID: ISSN 0013-4651
Publisher:
The Electrochemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; CALPHAD; Lanthanum strontium cobalt ferrite (LSCF); Solid oxide fuel cell (SOFC); SrZrO3 (SZO); Yttria stabilized zirconia (YSZ)

Citation Formats

Lu, Zigui, Darvish, Shadi, Hardy, John, Templeton, Jared, Stevenson, Jeffry, and Zhong, Yu. SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering. United States: N. p., 2017. Web. doi:10.1149/2.0141710jes.
Lu, Zigui, Darvish, Shadi, Hardy, John, Templeton, Jared, Stevenson, Jeffry, & Zhong, Yu. SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering. United States. doi:10.1149/2.0141710jes.
Lu, Zigui, Darvish, Shadi, Hardy, John, Templeton, Jared, Stevenson, Jeffry, and Zhong, Yu. Wed . "SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering". United States. doi:10.1149/2.0141710jes. https://www.osti.gov/servlets/purl/1390433.
@article{osti_1390433,
title = {SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering},
author = {Lu, Zigui and Darvish, Shadi and Hardy, John and Templeton, Jared and Stevenson, Jeffry and Zhong, Yu},
abstractNote = {This work probes the formation of SrZrO3 at the SDC/YSZ interface (Sm doped ceria, SDC; Y stabilized zirconia, YSZ) during (La1-xSrx)1-δCo1-yFeyO3 (LSCF) cathode sintering. SEM/EDS and grazing incidence X-ray diffraction results of annealed LSCF and YSZ samples reveal that even without physical contact between LSCF and YSZ, SrZrO3 was formed on the surface of YSZ, preferentially at the grain boundaries. It was suspected that the SrZrO3 formation is due to the Sr-containing gas species diffused through the pores of the SDC layer and reacted with the YSZ electrolyte. Computational thermodynamics was adopted to predict the gas species formed in air during sintering by using the La-Sr-Co-Fe-O-H thermodynamic database. Sr(OH)2 is identified as the dominant Sr-containing gas species under the experimental conditions. In addition, it was found that A-site deficiency in LSCF could effectively suppress the SrZrO3 formation while a dense and pore-free SDC interlayer is required to totally block the SrZrO3 formation. As a result, cell performance was significantly improved for a cell with a dense SDC interlayer fabricated by pulsed laser deposition, due to elimination of SrZrO3 formation and therefore reduced interfacial resistance.},
doi = {10.1149/2.0141710jes},
journal = {Journal of the Electrochemical Society},
number = 10,
volume = 164,
place = {United States},
year = {Wed Jul 19 00:00:00 EDT 2017},
month = {Wed Jul 19 00:00:00 EDT 2017}
}

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Cited by: 2works
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  • Density functional theory (DFT) based investigation of two parameters of prime interest -- oxygen vacancy and surface terminations along (100) and (110) planes -- has been conducted for La (1-x)Sr xFe(1-y)Co yO (3-more » $$\delta$$) perovskite oxides in view of their application towards thermochemical carbon dioxide conversion reactions. The bulk oxygen vacancy formation energies for these mixed perovskite oxides are found to increase with increasing lanthanum and iron contents in the 'A' site and 'B' site, respectively. Surface terminations along (100) and (110) crystal planes are studied to probe their stability and their capabilities to accommodate surface oxygen vacancies. Amongst the various terminations, the oxygen-rich (110) surface and strontium-rich (100) surface are the most stable, while transition metal-rich terminations along (100) revealed preference towards the production of oxygen vacancies. The carbon dioxide adsorption strength, a key descriptor for CO 2 conversion reactions, is found to increase on oxygen vacant surfaces thus establishing the importance of oxygen vacancies in CO 2 conversion reactions. Amongst all the surface terminations, the lanthanum-oxygen terminated surface exhibited the strongest CO 2 adsorption strength. Finally, the theoretical prediction of the oxygen vacancy trends and the stability of the samples were corroborated by the temperature-programmed reduction and oxidation reactions and in situ XRD crystallography.« less
  • Strontium doped lanthanum cobalt ferrite (LSCF) is a widely used cathode material due to its high electronic and ionic conductivity, and reasonable oxygen surface exchange coefficient. However, LSCF can have long-term stability issues such as surface segregation of Sr during solid oxide fuel cell (SOFC) operation, which can adversely affect the electrochemical performance. Thus, understanding the nature of the Sr surface segregation phenomenon, and how it is affected by the composition of LSCF and strain are critical. In this research, heteroepitaxial thin films of La 1-x Sr xCo 0.2Fe 0.8O 3 - with varying Sr content (x = 0.4, 0.3,more » 0.2) were deposited by pulsed laser deposition (PLD) on single crystal NdGaO 3, SrTiO 3 and GdScO 3 substrates, leading to different levels of strain in the films. The extent of Sr segregation at the film surface was quantified using synchrotron-based total reflection x-ray fluorescence (TXRF), and atomic force microscopy (AFM). The electronic structure of the Sr-rich phases formed on the surface was investigated by hard X-ray photoelectron spectroscopy (HAXPES). The extent of Sr segregation was found to be a function of the Sr content in bulk. Lowering the Sr content from 40% to 30% reduced the surface segregation, but further lowering the Sr content to 20% increased the segregation. The strain of LSCF thin films on various substrates was measured using high-resolution x-ray diffraction (HRXRD) and the Sr surface segregation was found to be reduced with compressive strain and enhanced with tensile strain present within the thin films. A model was developed correlating the Sr surface segregation with Sr content and strain effects to explain the experimental results.« less
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