Otto Schott Institute

Germany

Otto Schott Institute

Germany

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Zscheckel T.,Otto Schott Institute | Wisniewski W.,Otto Schott Institute | Russel C.,Otto Schott Institute
Advanced Functional Materials | Year: 2012

Polycrystalline ZnS samples are studied using X-ray diffraction and scanning electron microscopy including electron backscatter diffraction (EBSD). The material is industrially produced by a chemical vapor deposition process (CVD). Near the substrate, crystal growth leads to grains smaller than 50 μm in the cut plane. Elongated crystals with visible lengths of up to 400 μm are formed further from the substrate. These crystals are heavily twinned and exhibit Σ3 grain boundaries (i.e., the orientation of one {111}-plane is constant while rotations of 60° around its normal occur). About 1000 μm from the substrate, the grain size shrinks to about 20 μm along an abrupt border; a continuous grain size transition is not observed. Gradual orientation changes within single grains occur and in some cases lead to the fragmentation of grains parallel to the direction of growth. This is preferably observed in smaller grains more than 1000 μm from the substrate. Twinning, on the other hand, predominantly occurs in the large grains near the substrate. Both mechanisms should contribute to stress minimization in the sample. Textures of the analyzed surfaced indicate a general <001>-orientation perpendicular to the substrate and thus parallel to the direction of crystal growth. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Zscheckel T.,Otto Schott Institute | Kreher-Hartmann B.,Institute For Geowissenschaften | Russel C.,Otto Schott Institute
Journal of Physics and Chemistry of Solids | Year: 2016

A sample of natural zinc sulfide containing iron (from Portugal, Albergaria, Velha) was systematically investigated with respect to its microstructure using XRD (X-ray diffraction) and EBSD (electron back scatter diffraction). The habitus of the black sample suggests a hexagonal crystal structure, i.e. the occurrence of the Wurtzite phase. Nevertheless, using XRD and EBSD allowed only detecting and localizing the cubic Zincblende structure within the sample with the fibrous habitus while the expected hexagonal Wurtzite structure and possibly a hexagonal FeS structure were missed. The macroscopic fibrous structures consist of non-uniform and elongated grain structures which possess a preferred orientation with the <224>-direction parallel to the fiber direction. Inside the grains, twinning occurs (Σ3-Twinning) as well as grain fragmentation. Iron is not distributed homogeneously; instead areas with unique iron concentrations occurred. They were arranged like twins with iron concentrations from 4.1 up to 5.1 at% as detected and localized using energy dispersive x-ray spectroscopy (EDS). Fe2+ is incorporated in lattice sites of Zn2+. Although the phase diagram FeS-Zn-S is not yet completely determined in all composition ranges of interest, coexisting phases (zincblende and FeS) should be expected at room temperatures. The results may contribute to further insights into the growth mechanisms of natural zinc sulfide, respectively to the discussion about. Furthermore, it was shown, that the crystal habitus not always allows concluding on the crystals symmetry with certainty. © 2016 Elsevier Ltd. All rights reserved.

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