BaGe₈As₁₄: a semiconducting sodalite-type compound

Abstract

The new semiconducting sodalite-type BaGe8As14 compound exhibits a narrow band gap, low resistivity and partially disordered atom positions as good prerequisites for a thermoelectric material.

New Noncentrosymmetric Tetrel Pnictides Composed of Square‐Planar Gold(I) with Peculiar Bonding

“…This solution showed af ully occupied Au site and am ixed occupancy of the 8f Ge/ As site, with site occupancyf actorso f0 .6(1)/0.4, respectively. Despite the mixed occupancy of Ge and As being reported, [19] in mostc ases, Ge and As prefer to occupy separate atomic sites. [20][21][22][23][24][25] In the NCS space group Cc (no.…”

“…15), [18] with one Au site at position4 c and one mixed occupancy site of 50 %G ea nd 50 %A sa tg eneral position8 f. However, similar scattering factors for Ge and As make establishmento ft he correct space group challenging. [19,20] To find the true space group, high-resolutions ingle- crystal XRD datasets were collected (sin q max /l = 0.90 À1 )a nd solved in both space groups, Cc and C2/c. Initial refinement of our AuGeAs single-crystal diffraction dataset in the reported C2/c space group resulted in an R 1 value of 0.019 and an unusually low goodness-of-fit value of 0.85.…”

High Thermoelectric Properties in the Sodalite Compounds BaGe8As14 and AGe7As15 (A = Rb, Cs)

“…The new compounds crystallize with a sodalite-type structure isotypic to BaGe 8 As 14 . A Ge 24 β-cage (Figure a) is the core structure of the polyanionic network of vertex sharing GeAs 4 tetrahedra (Figure b).…”

“…The latter exhibits a static disorder by displacing the barium atoms off the high-symmetry (4̅3 m ) site at the cage centers. This is evident from a non-zero extrapolation of the thermal displacement parameter U eq to about 0.89 at T = 0 . The effect is absent in RbGe 7 As 15 and CsGe 7 As 15 , where the U eq extrapolates to 0.01 and 0.005, respectively (Figure ).…”

“…However, related cage compounds with networks made of heavier main group elements offer beneficial conditions for thermoelectric materials. Following this idea, we recently reported on the synthesis and crystal structure of the sodalite compound BaGe 8 As 14 and its possible thermoelectric properties . Indeed, it exhibits all of the aforementioned conditions favoring a low lattice thermal conductivity κ L .…”