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

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 7; no. 48; pp. 15188 - 15196
• Main Authors: Groß, H, Dankwort, T, Hansen, A.-L, Schürmann, U, Duppel, V, Poschmann, M, Meingast, A, Groeneveld, D, König, J, Bensch, W, Kienle, L
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 2019
• Subjects: Domains; Electron beams; Electron irradiation; N-type semiconductors; Organic chemistry; Plasma sintering; Power factor; Room temperature; Seebeck effect; Spark plasma sintering; Thermoelectric materials
• DOI: 10.1039/c9tc04548a
• ISSN: 2050-7526

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 Cr 3 S 4 -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 . 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.