Enhanced thermoelectric performance of In-substituted GeSb6Te10 with homologous structure

Abstract

We studied the crystal structure and thermoelectric properties of polycrystalline GeInxSb6−xTe10 (x = 0, 0.18, 0.3, and 0.6). Rietveld and Le Bail analyses showed that all compositions crystallized in trigonal structures with a 51-layer period. Substituting In decreased both the lattice and electronic thermal conductivity, as well as markedly increased the Seebeck coefficient. We ascribed this increase to increases in the effective mass of the carriers, likely caused by the formation of additional energy states near the Fermi level. In GeIn0.6Sb5.4Te10, we found a maximum ZT of 0.75 at 710 K, 1.9 times higher than that of GeSb6Te10.

Formation Phases and Electrical Properties of Ge-Bi-Te Compounds with Homologous Structures

“…The second model is basically referred to as the structure refined by Dr. Matsunaga. 6,9 In his model, the Te atoms occupy specific layers and the Ge and Bi atoms occupy the remaining layers in partial atomic disorder (hereafter referred to as Model 2). In our model, the fraction of Ge and Bi refined by Dr. Matsunaga 6,9 was used on every cation site.…”

“…6,9 In his model, the Te atoms occupy specific layers and the Ge and Bi atoms occupy the remaining layers in partial atomic disorder (hereafter referred to as Model 2). In our model, the fraction of Ge and Bi refined by Dr. Matsunaga 6,9 was used on every cation site. For In, we hypothesized that In was substituted in every Bi-site in equal proportion to retain a nominal composition.…”

“…We predicted that the lattice volume V would decrease with increasing In concentration 6,9 Red, green, and blue spheres represent Ge, Bi, and Te atoms. S5 and S7 are five-layer Bi 2 Te 3 -type slabs and seven-layer GeBi 2 Te 4 -type slabs, respectively.…”

“…5 Additionally, the effects of elemental substitution in this material have not yet been clarified. In our previous studies, we evaluated the crystal structure and TE properties of Insubstituted GeSb 6 Te 10 at 310-710 K. 6,7 We found that substituting In for Sb decreased j and enhanced S to yield a maximum ZT of 0.75 at 710 K for GeIn 0.6 Sb 5.4 Te 10 , which is 1.9 times higher than that of pure GeSb 6 Te 10 . 6 In this study, we focused on Insubstituted GeBi 6 Te 10 .…”

“…In our previous studies, we evaluated the crystal structure and TE properties of Insubstituted GeSb 6 Te 10 at 310-710 K. 6,7 We found that substituting In for Sb decreased j and enhanced S to yield a maximum ZT of 0.75 at 710 K for GeIn 0.6 Sb 5.4 Te 10 , which is 1.9 times higher than that of pure GeSb 6 Te 10 . 6 In this study, we focused on Insubstituted GeBi 6 Te 10 . As a result, we found that all samples prepared in this study contained two different periodic structures: GeBi 6 Te 10 and GeBi 4 Te 7 , as shown in Fig.…”