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@ARTICLE{Martin:9108,
      author       = {Martin, M. and Dronskowski, R. and Janek, J. and Becker,
                      K.-D. and Roehrens, D. and Brendt, J. and Lumey, M.W. and
                      Nagarajan, L. and Valov, I. and Börger, A.},
      title        = {{T}hermodynamics, structure and kinetics in the system
                      {G}a-{O}-{N}},
      journal      = {Progress in solid state chemistry},
      volume       = {37},
      issn         = {0079-6786},
      address      = {Oxford [u.a.]},
      publisher    = {Pergamon Press},
      reportid     = {PreJuSER-9108},
      year         = {2009},
      note         = {Financial support by the German Research Foundation (DFG
                      Priority Program 1136, Substitutional Effects in Ionic
                      Solids) is gratefully acknowledged. The authors would like
                      to express their gratitude to A. Shenyshin and M. Hoelzel
                      (FRIVIII, Garching) for their support during the neutron
                      measurements at the SPODI diffractometer, M. Lerch (FU
                      Berlin) for the quantitative analysis of nitrogen and oxygen
                      via the hot gas extraction method, G. Heger, G. Roth and K.
                      Sparta (AIXTAL, Aachen) for support in all crystallographic
                      matters, E. Welter, K. Rickers, A. Webb and D. Zajac (all
                      HASYLAB @ DESY) for support during the beam times, R.
                      Zaunbrecher for making the SEM measurements, F. Dorn and T.
                      Weirich},
      abstract     = {Within the ternary system Ga-O-N we performed experimental
                      and theoretical investigations on the thermodynamics,
                      structure and kinetics of new stable and metastable
                      compounds.We studied the ammonolysis of beta-Ga2O3 at
                      elevated temperatures by means of ex situ X-ray diffraction,
                      ex situ neutron diffraction, and in situ X-ray absorption
                      spectroscopy (XAS). From total diffraction pattern
                      refinement with the Rietveld method we analyzed the anionic
                      occupancy factors and the lattice parameters of beta-Ga2O3
                      during the reaction. Within the detection limits of these
                      methods, we can rule out the existence of a crystalline
                      oxynitride phase that is not derived from wurtzite-type GaN.
                      The nitrogen solubility in beta-Ga2O3 was found to be below
                      the detection limit of about 2-3 $at.\%$ in the anionic
                      sublattice. The kinetics of the ammonolysis of beta-Ga2O3 to
                      alpha-GaN and of the oxidation of alpha-GaN to beta-Ga2O3
                      was studied by means of in situ X-ray absorption
                      spectroscopy. In both cases the reaction kinetics could be
                      described well by fitting linear combinations of beta-Ga2O3
                      and alpha-GaN spectra only, excluding that other crystalline
                      or amorphous phases appear during these reactions. The
                      kinetics of the ammonolysis can be described well by an
                      extended Johnson-Mehl-Avrami-Kolmogorow model with
                      nucleation and growth of GaN nuclei, while the oxidation
                      kinetics can be modeled by a shrinking core model where
                      Ga2O3 grows as a layer. Investigations by means of TEM and
                      SEM support the assumptions in both models. To investigate
                      the structure and energetics of spinel-type gallium
                      oxynitrides (gamma-galons) we performed first-principles
                      calculations using density-functional theory. In addition to
                      the ideal cubic gamma-Ga2O3 we studied gallium deficient
                      gamma-galons within the Constant-Anion-Model.In highly
                      non-stoichiometric, amorphous gallium oxide of approximate
                      composition GaO1.2 we found at a temperature around 670 K an
                      insulator-metal transition, with a conductivity jump of
                      seven orders of magnitude. We demonstrate through
                      experimental studies and density-functional theory
                      calculations that the conductivity jump takes place at a
                      critical gallium concentration and is induced by
                      crystallization of stoichiometric beta-Ga2O3 within the
                      metastable oxide matrix. By doping with nitrogen the
                      critical temperature and the conductivity in the highly
                      conducting state can be tuned. (C) 2009 Elsevier Ltd. All
                      rights reserved.},
      keywords     = {J (WoSType)},
      cin          = {IFF-6 / JARA-FIT},
      ddc          = {540},
      cid          = {I:(DE-Juel1)VDB786 / $I:(DE-82)080009_20140620$},
      pnm          = {Grundlagen für zukünftige Informationstechnologien},
      pid          = {G:(DE-Juel1)FUEK412},
      experiment   = {EXP:(DE-MLZ)SPODI-20140101},
      shelfmark    = {Chemistry, Inorganic $\&$ Nuclear},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000273097800005},
      doi          = {10.1016/j.progsolidstchem.2009.11.005},
      url          = {https://juser.fz-juelich.de/record/9108},
}