Local structural distortions and reduced thermal conductivity in Ge-substituted chalcopyrite

Abstract

Chalcopyrite, CuFeS2 is considered one of the promising n-type thermoelectric materials with high natural abundancy as a mineral. In this work, a partial substitution of germanium in CuFeS2 (CuFe1-xGexS2, 0.0...

Enhancement of thermoelectric properties of CuFeS2 through formation of spinel-type microprecipitates

“…2c and S2†), the presence of which in the pristine phase has been previously established. 29,30 The energy of the absorption edge and the profile of the chromium spectra in the Cr-containing samples (Fig. 1d) is similar to that in the chromium spectrum of the NiCr 2 S 4 standard, suggesting that chromium is present in the +3 oxidation state, in an octahedral coordination with sulfur atoms.…”

“…Scanning electron microscopy (SEM) images of all Cr-containing materials, provided in Fig. S3† (the microstructural characterization for x = 0 sample is available in Tippireddy et al 30 ), show micro-sized precipitates of a secondary phase within the chalcopyrite matrix. These precipitates possess lamellar-like features similar to PbTe-based composites 66,67 and have not been observed in other substituted CuFeS 2 compounds.…”

Insights of Peculiar Green-Yellow Emission Occurrence in Ce3+-Doped Barium Yttrium Orthogermanate Phosphors

“…The proportion of oxygen vacancies vs lattice concentration increased with a gradual enhancement in the flux quantity and reduction atmosphere for the Ba 8.8 Ce 0.1 Na 0.1 Y 2 Ge 6 O 24 phosphors. As shown in Figure b, the 3d spectra of Ge show mixed oxidation states of Ge 4+ (3d 3/2 and 3d 5/2 ) and Ge 2+ (3d 3/2 and 3d 5/2 ) . When a reduction gas was introduced, the Ge 2+ /Ge 4+ oxidation ratio in the host lattice increased.…”

“…As shown in Figure 4b, the 3d spectra of Ge show mixed oxidation states of Ge 4+ (3d 3/2 and 3d 5/2 ) and Ge 2+ (3d 3/2 and 3d 5/2 ). 26 When a reduction gas was introduced, the Ge 2+ /Ge 4+ oxidation ratio in the host lattice increased. The normalized Ge K-edge XANES spectra of Ba 9 Y 2 Ge 6 O 24 (2.5/air) and Ba 8.8 Ce 0.1 Na 0.1 Y 2 Ge 6 O 24 (2.5/red and 7.5/red) with a standard Ge foil and GeO 2 precursor are shown in Figure 4c.…”

Influence of Ge Lone Pairs on the Elasticity and Thermal Conductivity of GeSe–AgBiSe2 Alloys

“…Because the (GeSe) 1– x –(AgBiSe 2 ) x system exhibits three important crystal structures, it provides a platform for understanding and decoupling the effect of the composition and crystal structure on κ L . Notable prior investigations across various material families − have discussed the importance of Ge lone pairs in heat transport. Nevertheless, these earlier studies have predominantly overlooked a crucial aspect: the substantial stiffening that accompanies the martensitic rhombohedral-to-cubic phase transition.…”