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@PHDTHESIS{Bakan:279914,
      author       = {Bakan, Emine},
      title        = {{Y}ttria-{S}tabilized {Z}irconia / {G}adolinium {Z}irconate
                      {D}ouble-{L}ayer {P}lasma-{S}prayed {T}hermal {B}arrier
                      {C}oating {S}ystems ({TBC}s)},
      volume       = {294},
      school       = {Ruhr-Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2015-07788},
      isbn         = {978-3-95806-100-2},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {vi, 132 S.},
      year         = {2015},
      note         = {Ruhr-Universität Bochum, Diss., 2015},
      abstract     = {Thermal barrier coating (TBC) research and development is
                      driven by the desirability of further increasing the maximum
                      inlet temperature in a gas turbine engine. A number of new
                      top coat ceramic materials have been proposed during the
                      last decades due to limited temperature capability (1200
                      °C) of the state-of-the-art yttria-stabilized zirconia (7
                      wt. \%Y$_{2}$O$_{3}$-ZrO$_{2}$, YSZ) at long term operation.
                      Zirconate pyrochlores of the large lanthanides((Gd
                      $\rightarrow$ La)$_{2}$Zr$_{2}$O$_{7}$) have been
                      particularly attractive due to their higher temperature
                      phase stability than that of the YSZ. Nonetheless, the
                      issues related with the implementation of pyrochlores such
                      as low fracture toughness and formation of deleterious
                      interphases with thermally grown oxide (TGO,
                      Al$_{2}$O$_{3}$) were reported. The implication was the
                      requirement of an interlayer between the pyrochlores and
                      TGO, which introduced double-layer systems to the TBC
                      literature. Furthermore, processability issues of
                      pyrochlores associated with the different evaporation rates
                      of lanthanide oxides and zirconia resulting in unfavorable
                      composition variations in the coatings were addressed
                      indifferent studies. After all, although the material
                      properties are available, there is a paucity of data in the
                      literature concerning the properties of the coatings made of
                      pyrochlores. From the processability point of view the most
                      reported pyrochlore is La$_{2}$Zr$_{2}$O$_{7}$. Hence, the
                      goal of this research was to investigate plasma-sprayed
                      Gd$_{2}$Zr$_{2}$O$_{7}$ (GZO) coatings and YSZ/GZO
                      double-layer TBC systems. Three main topics were examined
                      based on processing, performance and properties: (i) the
                      plasma spray processing of the GZO and its impact on the
                      microstructural and compositional properties of the GZO
                      coatings; (ii) the cycling lifetime of the YSZ/GZO
                      double-layer systems under thermal gradient at a surface
                      temperature of 1400 °C; (iii) the properties of the GZO and
                      YSZ coatings such as thermal conductivity, coefficient of
                      thermal expansion as well as time and temperature-dependent
                      elastic and creep deformations. Thermal cycling results
                      displayed that the double-layer YSZ/GZO TBC concept is able
                      to provide signicant lifetime improvement at 1400 °C
                      surface temperature compared to the standard YSZ. The
                      investigations on the chemical composition of the as-sprayed
                      GZO revealed that no signicant gadolinia evaporation, which
                      would compromise the performance of the coating, takes place
                      in the examined spray current range (300 A-525 A). The
                      detailed examination of microstructural properties of the
                      as-sprayed GZO highlighted the importance of the process
                      parameters for achieving the desired porosity features
                      assisting superior lifetime performances. A signicant
                      insight was gained intothe elastic and creep deformation of
                      the plasma-sprayed YSZ and GZO coatings which play a
                      critical role on the development of advanced TBCs. The
                      overarching conclusion of this work is that the GZO has the
                      potential to increase the temperature capability of
                      gasturbines, if it is applied in double-layer TBC systems
                      and if its microstructure is tailoredby adapted processing.},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {113 - Methods and Concepts for Material Development
                      (POF3-113) / HITEC - Helmholtz Interdisciplinary Doctoral
                      Training in Energy and Climate Research (HITEC)
                      (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-113 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
      url          = {https://juser.fz-juelich.de/record/279914},
}