A New Material with a Composite Crystal Structure Causing Ultralow Thermal Conductivity and Outstanding Thermoelectric Properties: Tl2Ag12Te7+δ

• DOI: 10.1021/jacs.8b04639
• Publication Date: 2018-06-17T15:48:11Z
• Authors: Yixuan Shi; Abdeljalil Assoud; Simeon Ponou; Sven Lidin; Holger Kleinke
• Keywords: Substructure; Chain (unit); Figure of Merit

A new state-of-the-art thermoelectric material, Tl2Ag12Te7+δ, which possesses an extremely low thermal conductivity of about 0.25 W m–1 K–1 and a high figure-of-merit up to 1.1 at 525 K, was obtained using conventional solid-state reaction approach. Its subcell is variant the Zr2Fe12P7 type, but ultimately its structure refined as composite Tl2Ag12Te6 framework linear Te atom chain running along c axis. The super-space group determined be P63(00γ)s with = b 11.438(1) Å, 4.6256(5) that substructure has same axes, 3.212(1) space P6(00γ)s. modulation leads formation Te2 Te3 fragments in this formula Tl2Ag11.5Te7.4. consists complex network three-dimensionally connected AgTe4 tetrahedra forming channels filled Tl atoms. electronic structures four different models comprising chains, Tl2Ag12Te7, Tl2Ag12Te7.33, 2× Tl2Ag12Te7.5, were computed WIEN2k package. Depending on content within chain, are either semiconducting or metallic. Physical property measurements revealed properties, ultralow conductivity, excellent properties elevated temperatures.