Structure and thermoelectric properties of the n-type clathrate Ba8Cu5.1Ge40.2Sn0.7

We study type I clathrate Ba8Cu5.1Ge40.2Sn0.7 single crystals (space group Pmn, no. 223, a = 10.7151(3)) grown using a Sn flux method. Microprobe analysis and single-crystal X-ray diffraction reveal a small amount of Sn embedded in the Cu/Ge framework, which increases disorder at the guest Ba sites. Ba8Cu5.1Ge40.2Sn0.7 is diamagnetic with a susceptibility of ∼2.8 × 10−7 emu g−1 and shows metal-like behavior (dρ/dT > 0) with a low charge carrier concentration of 0.5 e− per unit cell at 300 K. The single crystals show a relatively high carrier mobility (μ (300 K) = 11.9 cm2 V−1) and very low lattice thermal conductivity (∼0.6 W m−1 K−1). The thermoelectric figure of merit ZT of Ba8Cu5.1Ge40.2Sn0.7 single crystals reaches a maximum value of 0.6 at 773 K, which can be further improved by adjusting the chemical composition.

[1]  T. Nakayama,et al.  Phonon-glass electron-crystal thermoelectric clathrates : Experiments and theory , 2014, 1402.5756.

[2]  E. Bauer,et al.  Tuning of band gap and thermoelectric properties of type-I clathrate Ba8NixZnyGe46−x−y−zSnz , 2013 .

[3]  E. Bauer,et al.  Structural and thermoelectric properties of Ba8Cu5SixGe41−xclathrates , 2013 .

[4]  E. Bauer,et al.  Influence of Sn-substitution on the thermoelectric properties of the clathrate type-I, Ba8Zn(x)Ge(46-x-y)Sn(y). , 2013, Dalton transactions.

[5]  Jingtao Xu,et al.  Heat capacity studies on rattling vibrations in Ba-TM-Ge type I clathrates , 2012 .

[6]  R. Podloucky,et al.  Phase equilibria, crystal chemistry, electronic structure and physical properties of Ag–Ba–Ge clathrates , 2011 .

[7]  M. Yamashita,et al.  Heat Capacity Study on Anharmonicity in Ae8Ga16Ge30 (Ae = Sr and Ba) , 2011 .

[8]  E. Bauer,et al.  Phase Equilibria, Crystal Chemistry, and Physical Properties of Ag–Ba–Si Clathrates , 2011 .

[9]  M. Schmidt,et al.  Atomic interactions in the p-type clathrate I Ba8Au5.3Ge40.7. , 2011, Inorganic chemistry.

[10]  M. Chi,et al.  On the Design of High‐Efficiency Thermoelectric Clathrates through a Systematic Cross‐Substitution of Framework Elements , 2010 .

[11]  H. Borrmann,et al.  Atomic ordering and thermoelectric properties of the n-type clathrate Ba8Ni3.5Ge42.1square0.4. , 2010, Dalton transactions.

[12]  H. Borrmann,et al.  Crystal structure and transport properties of Ba8Ge43square3. , 2010, Dalton transactions.

[13]  B. Iversen,et al.  Thermoelectric clathrates of type I. , 2010, Dalton transactions.

[14]  Eric S. Toberer,et al.  Characterization and analysis of thermoelectric transport in n-type Ba_(8)Ga_(16−x)Ge_(30+x) , 2009 .

[15]  P. Rogl,et al.  The clathrate Ba8CuxGe46−x−y□y: Phase equilibria and crystal structure , 2009 .

[16]  Jingtai Zhao,et al.  Structure and low temperature physical properties of Ba8Cu6Ge40 , 2009 .

[17]  M. Christensen,et al.  Clathrate guest atoms under pressure , 2009 .

[18]  P. Simon,et al.  Germanium Vacancies and Charge Transport Properties in Ba8ZnxGe46−x−y◻y , 2009 .

[19]  Hannu Mutka,et al.  Breakdown of phonon glass paradigm in La- and Ce-filled Fe4Sb12 skutterudites. , 2008, Nature materials.

[20]  Kim Lefmann,et al.  Avoided crossing of rattler modes in thermoelectric materials. , 2008, Nature materials.

[21]  G. J. Snyder,et al.  High temperature thermoelectric efficiency in Ba8Ga16Ge30 , 2008 .

[22]  M. Rotter,et al.  Structure and physical properties of type-I clathrate solid-solution Ba 8 Pt x Ge 46 − x − y ◻ y ( ◻ = vacancy ) , 2007 .

[23]  M. Rotter,et al.  Clathrate formation in the Ba-Pd-Ge system : Phase equilibria, crystal structure, and physical properties , 2007 .

[24]  M. Rotter,et al.  Ternary clathrates Ba–Cd–Ge: phase equilibria, crystal chemistry and physical properties , 2007 .

[25]  M. Nygren,et al.  Crystal structure, band structure, and physical properties of Ba8Cu6-xGe40+x (0 < x < 0.7) , 2006 .

[26]  G. Stucky,et al.  Large thermoelectric figure of merit at high temperature in Czochralski-grown clathrate Ba8Ga16Ge30 , 2006 .

[27]  H. Anno,et al.  Effect of Cu Substitution on Thermoelectric Properties of Ge Clathrates , 2005 .

[28]  W. Gou,et al.  Structure and stability of Ba–Cu–Ge type-I clathrates , 2002, cond-mat/0210244.

[29]  O. Zhou,et al.  Electronic structure of Si and Ge gold-doped clathrates , 1999 .

[30]  Louis J. Farrugia,et al.  WinGX suite for small-molecule single-crystal crystallography , 1999 .

[31]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[32]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[33]  Hafner,et al.  Ab initio molecular dynamics for liquid metals. , 1995, Physical review. B, Condensed matter.

[34]  G. Cordier,et al.  Neue ternäre intermetallische Verbindungen mit Clathratstruktur: Ba8(T,Si)6Si40 und Ba6(T,Ge)6Ge40 mit T ≡ Ni, Pd, Pt, Cu, Ag, Au , 1991 .

[35]  Brian H. Toby,et al.  EXPGUI, a graphical user interface for GSAS , 2001 .