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@INPROCEEDINGS{Mller:887780,
      author       = {Müller, David},
      title        = {{T}here is no {F}e4+: {W}hat {X}-{R}ay spectroscopy can
                      tell you about point defects (and what not)},
      reportid     = {FZJ-2020-04417},
      year         = {2020},
      abstract     = {Charged point defects are an integral part of defect
                      equilibria in solid state ionics, especially when reactions
                      with a gas or liquid are involved. With the advent of X-ray
                      spectroscopic methods made possible in atmospheres
                      approaching ambient pressure and at elevated temperatures it
                      has become tempting to observe these ions and their charge
                      states directly as surface and bulk redox processes take
                      place. Though with the right checks and balances this
                      approach can give, and has given, invaluable insights into
                      mechanisms governing electrochemical properties of solids
                      and their interaction with gases and liquids, it has also
                      led to many misconceptions. In this presentation, I will use
                      prototypical materials such as (La,Sr)(Fe,Co)O3-δ and
                      Sr(Ti,Co)O3-δ utilized in solid state electrochemistry to
                      showcase the strengths and limitations of in situ X-Ray
                      absorption (XAS) and photoemission spectroscopy (XPS). The
                      secession from using XAS and XPS to (attempt to) simply
                      determine formal oxidation states as a function of
                      temperature, chemistry and atmosphere has, for example, led
                      to recognition of the role of the transition metal in the
                      perovskite structure in the former and peculiarities in the
                      conductions mechanism of the latter compound.},
      month         = {Jan},
      date          = {2020-01-22},
      organization  = {Electronic Materials and Applications,
                       Orlando, FL (USA), 22 Jan 2020 - 24 Jan
                       2020},
      subtyp        = {Invited},
      cin          = {PGI-6},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {522 - Controlling Spin-Based Phenomena (POF3-522)},
      pid          = {G:(DE-HGF)POF3-522},
      typ          = {PUB:(DE-HGF)6},
      url          = {https://juser.fz-juelich.de/record/887780},
}