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Purification by SPS and formation of a unique 3D nanoscale network: The showcase of Ni-Cr-S

 
: Groß, Hendrik; Dankwort, Torben; Hansen, Anna-Lena; Schürmann, Ulrich; Düppel, Viola; Poschmann, Michael; Meingast, Arno; Groeneveld, Dennis; König, Jan D.; Bensch, Wolfgang; Kienle, Lorenz

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Journal of materials chemistry. C, Materials for optical and electronic devices 7 (2019), No.48, pp.15188-15196
ISSN: 2050-7526
ISSN: 2050-7534
English
Journal Article
Fraunhofer IPM ()
thermoelectricity; spark plasma sintering; thermal conductivity; electrical conductivity; seebeck coefficient

Abstract
The occurrence of a unique 3D nanoscale network in Ni-Cr-S, treated via spark-plasma sintering, was discovered with a variety of ex situ and in situ TEM and XRD techniques. The starting material, consisting of a heterogeneous mixture of different phases, could be purified upon application of the sintering process. The obtained samples showed a network of chemically segregated domains being either Ni rich and Cr deficient or vice versa. These domains could be proven to intergrow fully coherently in 3D, thus establishing a unique microstructure. Electron beam irradiation caused the initial Cr3S4-type structures to transform into the disordered NiAs-type. The disordering is characterised by significant short-range ordering as indicated by the appearance of prominent diffuse scattering. Thermoelectric characterisation at room temperature indicated an n-type semiconductor behaviour with thermal and electrical conductivities similar to usual thermoelectric materials, however with a low Seebeck coefficient and a low power factor of 49.3 μW m-1 K-2.

: http://publica.fraunhofer.de/documents/N-572071.html