@article{RyllSchmitzdeBooretal.2018,
  author    = {Ryll, Britta and Schmitz, Andreas and de Boor, Johannes and Franz, Alexandra and Whitfield, Pamela S. and Reehuis, Manfred and Hoser, Andreas and M{\"u}ller, Eckhard and Habicht, Klaus and Fritscht, Katharina},
  title     = {Structure, phase composition, and thermoelectric properties of YbxCo4Sb12 and their dependence on synthesis method},
  series = {ACS applied energy materials},
  volume    = {1},
  journal   = {ACS applied energy materials},
  number    = {1},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {2574-0962},
  doi       = {10.1021/acsaem.7b00015},
  pages     = {113 -- 122},
  year      = {2018},
  abstract  = {We present a combined microscopic and macroscopic study of YbxCo4Sb12 skutterudites for a range of nominal filling fractions, 0.15 < x < 0.75. The samples were synthesized using two different methods — a melt-quench-annealing route in evacuated quartz ampoules and a non-equilibrium ball-mill route — for which we directly compare the crystal structure and phase composition as well as the thermoelectric properties. Rietveld refinements of high-quality neutron powder diffraction data reveal about a 30-40\% smaller Yb occupancy on the crystallographic 2a site than nominally expected for both synthesis routes. We observe a maximum filling fraction of at least 0.439(7) for a sample synthesized by the ball-mill routine, exceeding theoretical predictions of the filling fraction limit of 0.2-0.3. A single secondary phase of CoSb2 is observed in ball-mill-synthesized samples, while two secondary phases, CoSb2 and YbSb2, are detected for samples prepared by the ampoule route. A detrimental influence of the secondary phases on the thermoelectric properties is observed for secondary-phase fractions larger than 8 wt \% regardless of the kind of secondary phase. The largest figure of merit of all samples with a ZT ∼ 1.0 at 723 K is observed for the sample with a refined Yb content of x2a = 0.159(3), synthesized by the ampoule route.},
  language  = {en}
}
@article{FranzToebbensSteckhanetal.2018,
  author    = {Franz, Alexandra and T{\"o}bbens, Daniel M. and Steckhan, Julia and Schorr, Susan},
  title     = {Determination of the miscibility gap in the solid solutions series of methylammonium lead iodide/chloride},
  series = {Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials},
  volume    = {74},
  journal   = {Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials},
  publisher = {International Union of Crystallography},
  address   = {Chester},
  issn      = {2052-5206},
  doi       = {10.1107/S2052520618010764},
  pages     = {445 -- 449},
  year      = {2018},
  abstract  = {Perovskites are widely known for their enormous possibility of elemental substitution, which leads to a large variety of physical properties. Hybrid perovskites such as CH3NH3PbI3 (MAPbI(3)) and CH3NH3PbCl3 (MAPbCl(3)) are perovskites with an A([XII])B([VI)X(-)([II)(])structure, where A is an organic molecule, B is a lead(II) cation and X is a halide anion of iodine or chlorine. Whereas MAPbCl(3) crystallizes in the cubic space group Pm (3) over barm, MAPbI(3) is in the tetragonal space group I4/mcm. The substitution of I by Cl leads to an increased tolerance against humidity but is challenging or even impossible due to their large difference in ionic radii. Here, the influence of an increasing Cl content in the reaction solution on the miscibility of the solid solution members is examined systematically. Powders were synthesized by two different routes depending on the I:Cl ratio. High-resolution synchrotron X-ray data are used to establish values for the limits of the miscibility gap which are 3.1 (1.1) mol\% MAPbCl(3) in MAPI(3) and 1.0 (1) mol\% MAPbI(3) in MAPCl. The establishment of relations between average pseudo-cubic lattice parameters for both phases allows a determination of the degree of substitution from the observed lattice parameters.},
  language  = {en}
}