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@PHDTHESIS{Yin:857739,
      author       = {Yin, Xiaoyan},
      title        = {{A}ging and {D}egradation {B}ehavior of {E}lectrode
                      {M}aterials in {S}olid {O}xide {F}uel {C}ells ({SOFC}s)},
      volume       = {446},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2018-06707},
      isbn         = {978-3-95806-374-7},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {x, 103 S.},
      year         = {2018},
      note         = {RWTH Aachen, Diss., 2018},
      abstract     = {(La,Sr)(Co,Fe)O$_{3-δ}$ is one of the most potential
                      cathode materials for solid oxide fuel cell(SOFC)
                      applications. Sr in this type of cathode material is very
                      reactive to form secondary phases with other oxides, which
                      affect micro structures and properties of the cathode
                      material, the GDC layer and the ZrO$_{2}$-based electrolyte.
                      The Sr related degradation issues, Cr poisoning and volatile
                      Sr species formation, are studied. As supplement to existing
                      experimental knowledge on Cr poisoning, specific
                      thermodynamic aspects for Cr poisoning are discussed. The
                      thermodynamic calculations show that pCrO$_{3}$ has a
                      stronger temperature dependence than pCrO$_{2}$(OH)$_{2}$,
                      and when considering the reaction between SrO and
                      CrO$_{3}$(g), dependent on different pCrO$_{3}$ and local
                      pO$_{2}$ in the cathode, different Sr-Cr-O secondary phases
                      SrCrO$_{4}$,SrCrO$_{3}$, Sr$_{3}$Cr$_{2}$O$_{8}$ or
                      Sr$_{2}$CrO$_{4}$ could be formed. Additionally,
                      thermodynamic calculations show that in the presence of
                      water vapor, formation of volatile Sr(OH)$_{2}$ is possible
                      as well. pSr(OH)$_{2}$ depends on temperature, pH$_{2}$O and
                      SrO activity, and can be of the same order of magnitude as
                      pCrO$_{2}$(OH)$_{2}$. Volatile Sr(OH)$_{2}$ diffuse through
                      the porous GDC layer and react with ZrO$_{2}$-based
                      electrolytes to form SrZrO$_{3}$ precipitates. The reaction
                      between gaseous Sr species and an 8YSZ sheet is studied
                      experimentally. The surface of the 8YSZ sheet is
                      investigated by SEM coupled with EDS, confirming the
                      deposition of Sr. Since the reaction between the gaseous Sr
                      species and 8YSZ depends on theZrO$_{2}$ activity in 8YSZ,
                      the ZrO$_{2}$ activity in 8YSZ is measured by Knudsen
                      Effusion Mass Spectrometry. The measured aZrO$_{2}$ shows no
                      temperature dependence, which is around 0.85. A high
                      ZrO$_{2}$ activity in 8YSZ facilitates the reaction between
                      the gaseous Sr species and 8YSZ from a thermodynamic point
                      of view. In addition, first principles phonon calculations
                      combined with quasi-harmonic approximation (QHA) are used to
                      predict the thermal expansion of
                      La$_{0.5}$Sr$_{0.5}$Co$_{0.25}$Fe$_{0.75}$O$_{3}$ (LSCF55).
                      Within the framework of the QHA, the volumetric thermal
                      expansion coefficient of LSCF55 is calculated as
                      $\alpha_{𝑉,𝐺𝐺𝐴}$ = 50.34 ∗ 10$^{−6}$
                      𝐾$^{−1}$. For comparison, the lattice expansion and the
                      volume expansion of LSCF55 grain are measured by in-situ
                      high temperature X-ray diffractometer (HT-XRD). An
                      anisotropic thermal expansion of rhombohedral LSCF55 with
                      $\alpha_{𝑎,ℎ𝑒𝑥}$ = 10.89 ∗ 10$^{−6}$
                      𝐾$^{−1}$ and $\alpha_{𝑐,ℎ𝑒𝑥}$ = 21.18 ∗
                      10$^{−6}$ 𝐾$^{−1}$ is obtained. The volumetric
                      thermal expansion coefficient is measured as
                      $\alpha_{𝑉,𝐻𝑇−𝑋𝑅𝐷}$ = 43.17 ∗
                      10$^{−6}$ 𝐾$^{−1}$. Additionally, the effectively
                      isotropic expansion coefficients of a polycrystalline LSCF55
                      bar specimen are measured using a vertical high-performance
                      thermo-mechanical analyzer and yield
                      $\alpha_{𝑙,𝑏𝑎𝑟
                      𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛}$ = 17.37 ∗ 10$^{−6}$
                      𝐾$^{−1}$ and $\alpha_{𝑉,𝑏𝑎𝑟
                      𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛}$ = 52.11 ∗ 10$^{−6}$
                      𝐾$^{−1}$. A Good agreement between the calculated and
                      measured values of $\alpha_{𝑉}$ is obtained.},
      cin          = {IEK-2},
      cid          = {I:(DE-Juel1)IEK-2-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243) / 135 - Fuel Cells
                      (POF3-135)},
      pid          = {G:(DE-HGF)POF3-243 / G:(DE-HGF)POF3-135},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2019020600},
      url          = {https://juser.fz-juelich.de/record/857739},
}