Thermoelectric characterization of the clathrate-I solid solution Ba8− δ AuxGe46−x

Abstract

Clathrate-I-based materials are promising for waste-heat recovering applications via thermoelectric (TE) effects. However, the lack of highly efficient p-type materials hampers the development of clathrate-based TE devices. In this work, the synthesis of the p-type semiconductor Ba7.8Au5.33Ge40.67 with clathrate-I structure is up-scaled by steel-quenching and spark plasma sintering treatment at 1073 K. A thermoelectric figure of merit ZT ≈ 0.9 at 670 K is reproducibly obtained, and 40 chemically homogeneous module legs of 5 × 5 × 7 mm3 are fabricated. By using a carbon layer as a diffusion barrier, electrical contacts are sustainable at elevated application temperatures. Eight couples with the clathrate-I compounds Ba7.8Au5.33Ge40.67 as p-type and Ba8Ga16Ge30 as n-type materials are integrated into a TE module with an output power of 0.2 W achieved under a temperature difference ΔT = 380 K (T1 = 673 K and T2 = 293 K). The thermoelectric performance of Ba7.8Au5.33Ge40.67 demonstrates the potential of type-I clathrates for waste heat recycling.

Lithium metal atoms fill vacancies in the germanium network of a type-I clathrate: synthesis and structural characterization of Ba8Li5Ge41

“…For instance, type-I clathrates with nominal compositions Ba 8 T x Ge 46−x (T = Ga, Zn, Cd, Ni, Pd, Pt, Cu, Ag, and Au) have been studied and reported by us and by various groups. 13,25,[30][31][32]36,37,[46][47][48][49][50][51][52] In many of the latter cases, substitutions and vacancies coexist; the recent comprehensive investigation in the Ba-Au-Ge system is a testament to the level of complexity. 52 In contrast to the frequent studies on the substitution patterns with transition metal elements, clathrates containing Li remain under-explored.…”

“…13,25,[30][31][32]36,37,[46][47][48][49][50][51][52] In many of the latter cases, substitutions and vacancies coexist; the recent comprehensive investigation in the Ba-Au-Ge system is a testament to the level of complexity. 52 In contrast to the frequent studies on the substitution patterns with transition metal elements, clathrates containing Li remain under-explored. 63 The scarcity of the experimental data can be explained by the fact that the size of the Li atom makes it an unfavorable choice for a guest atom for incorporation into the large polyhedral cages.…”

“…For instance, type-I clathrates with nominal compositions Ba 8 T x Ge 46− x (T = Ga, Zn, Cd, Ni, Pd, Pt, Cu, Ag, and Au) have been studied and reported by us and by various groups. 13,25,30–32,36,37,46–52 In many of the latter cases, substitutions and vacancies coexist; the recent comprehensive investigation in the Ba–Au–Ge system is a testament to the level of complexity. 52…”

“…13,25,30–32,36,37,46–52 In many of the latter cases, substitutions and vacancies coexist; the recent comprehensive investigation in the Ba–Au–Ge system is a testament to the level of complexity. 52…”