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@ARTICLE{Bakan:892966,
      author       = {Bakan, Emine and Sohn, Yoo Jung and Vaßen, Robert},
      title        = {{M}icrostructure and {P}hase {C}omposition {E}volution of
                      {S}ilicon-{H}afnia {F}eedstock during {P}lasma {S}praying
                      and {F}ollowing {C}yclic {O}xidation},
      journal      = {Acta materialia},
      volume       = {214},
      issn         = {1359-6454},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {FZJ-2021-02465},
      pages        = {117007 -},
      year         = {2021},
      abstract     = {In this work, silicon–hafnia (Si-HfO2, 80/20 mol. $\%)$
                      feedstock was plasma sprayed for Environmental Barrier
                      Coating bond coat application. In the as-sprayed coating,
                      hafnium disilicide (HfSi2), HfO2 tetragonal (t), and cubic
                      (c) phases with a total volume of ~20 $\%$ were detected
                      together with Si and HfO2 monoclinic (m). The
                      temperature-dependent evolution of these phases was analyzed
                      and paired with microstructural observations. It was found
                      that above 700 °C, HfSi2 oxidizes and HfO2 (t) and (c)
                      transforms into (m) polymorph. Up to this temperature,
                      as-sprayed coating showed a non-linear expansion behavior.
                      Estimated volume expansion at ~750 °C was 3.6 $\%$ based on
                      dilatometry measurement. The primary and secondary
                      mechanisms leading to the expansion in the coating were
                      identified as oxidation of HfSi2 and polymorphic phase
                      transitions in HfO2, respectively. As a consequence of the
                      volume expansion, the coating was extensively cracked during
                      cyclic oxidation and hence not protective anymore. After 100
                      h at 1300 °C, the volume fraction of oxidation product SiO2
                      was significant in the coating (0.34), while HfO2 was
                      largely consumed (0.1) in the formation of HfSiO4 (0.56).
                      This result suggested that reversible α↔β phase
                      transitions in SiO2-cristobalite could be another factor
                      contributing to the cracking in the coating during cyclic
                      oxidation.},
      cin          = {IEK-1},
      ddc          = {670},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {124 - Hochtemperaturtechnologien (POF4-124)},
      pid          = {G:(DE-HGF)POF4-124},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000663791200010},
      doi          = {10.1016/j.actamat.2021.117007},
      url          = {https://juser.fz-juelich.de/record/892966},
}