Structure and Transport Properties of Dense Polycrystalline Clathrate-II (K,Ba)16(Ga,Sn)136 Synthesized by a New Approach Employing SPS

Kaya Wei; Xiaoyu Zeng; Terry M Tritt; Artem R Khabibullin; Lilia M Woods; George S Nolas

doi:10.3390/ma9090732

Structure and Transport Properties of Dense Polycrystalline Clathrate-II (K,Ba)₁₆(Ga,Sn)₁₃₆ Synthesized by a New Approach Employing SPS

Materials (Basel). 2016 Aug 26;9(9):732. doi: 10.3390/ma9090732.

Authors

Kaya Wei¹, Xiaoyu Zeng², Terry M Tritt³, Artem R Khabibullin⁴, Lilia M Woods⁵, George S Nolas⁶

Affiliations

¹ Department of Physics, University of South Florida, Tampa, FL 33620, USA. kayawei@mail.usf.edu.
² Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA. xzeng@g.clemson.edu.
³ Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA. ttritt@clemson.edu.
⁴ Department of Physics, University of South Florida, Tampa, FL 33620, USA. artem1@mail.usf.edu.
⁵ Department of Physics, University of South Florida, Tampa, FL 33620, USA. lmwoods@usf.edu.
⁶ Department of Physics, University of South Florida, Tampa, FL 33620, USA. gnolas@usf.edu.

Abstract

Tin clathrate-II framework-substituted compositions are of current interest as potential thermoelectric materials for medium-temperature applications. A review of the literature reveals different compositions reported with varying physical properties, which depend strongly on the exact composition as well as the processing conditions. We therefore initiated an approach whereby single crystals of two different (K,Ba)₁₆(Ga,Sn)₁₃₆ compositions were first obtained, followed by grinding of the crystals into fine powder for low temperature spark plasma sintering consolidation into dense polycrystalline solids and subsequent high temperature transport measurements. Powder X-ray refinement results indicate that the hexakaidecahedra are empty, K and Ba occupying only the decahedra. Their electrical properties depend on composition and have very low thermal conductivities. The structural and transport properties of these materials are compared to that of other Sn clathrate-II compositions.

Keywords: SPS processing; clathrate; thermoelectrics.