Re-evaluation of the electronic structure and thermoelectric properties of narrow-gap semiconducting α-SrSi2: A complementary experimental and first-principles hybrid-functional approach

Daishi Shiojiri,Motoharu Imai,Tsutomu Iida,Takuya Kodama,Kota Hiratsuka,Naomi Hirayama,Shinta Takahashi,Yuki Kayama,Seiya Yamaguchi,Tomoyuki Kadono,Masato Yamaguchi,Yoji Imai

doi:10.1063/5.0041670

Abstract

Thermoelectric power generation in the low temperature region has attracted considerable attention as a means of the effective use of distributed energy and for sensor applications. However, it is difficult to theoretically predict the exact thermoelectric transport properties owing to the relatively narrow bandgap of low temperature thermoelectric materials. In this study, a high-purity α-SrSi2 crystal was synthesized by the vertical Bridgman (VB) method. The carrier density of the VB-grown α-SrSi2 was investigated, and, from the temperature dependence of the carrier density, it was estimated that the bandgap was 13.1 meV. First-principles calculations using the Heyd–Scuseria–Ernzerhof screened hybrid functional for α-SrSi2 predicted the bandgap to be very close to this value (13.27 meV) when assuming the mixing parameter of the Hartree–Fock contribution to the exact exchange is 18.7%. Using the calculated electronic structure and the measured carrier concentration, the predicted temperature dependence of the Seebeck coefficient was in good agreement with the experimental results.

Highlights

The emerging global need for energy demand has intensified interest in more effective means of power generation
Using the calculated electronic structure and the measured carrier concentration, the predicted temperature dependence of the Seebeck coefficient was in good agreement with the experimental results
TE semiconductors, especially those operating at low temperatures, are expected to be applied to power generation systems that utilize the vaporization of liquefied natural gas and liquid nitrogen as cold heat energy sources,[1,2,3,4,5,6,7] and to self-powered wireless temperature sensors based on the Seebeck effect for investigating the behavior of the thermal energy from exhaust heat, including from humans, aiming to realize highly networked and connected societies.[8–12]

Summary

Introduction

The emerging global need for energy demand has intensified interest in more effective means of power generation. TE semiconductors, especially those operating at low temperatures, are expected to be applied to power generation systems that utilize the vaporization of liquefied natural gas and liquid nitrogen as cold heat energy sources,[1,2,3,4,5,6,7] and to self-powered wireless temperature sensors based on the Seebeck effect for investigating the behavior of the thermal energy from exhaust heat, including from humans, aiming to realize highly networked and connected societies.[8–12] Currently, Bi–Te- and Pb–Te-based materials, which are bulk high ZT materials operating in the low-temperature region, are put into scitation.org/journal/jap practical use as modules for thermoelectric power generation and Peltier cooling They contain toxic and rare elements in their base material composition; alternative earthabundant environmentally friendly materials with high thermoelectric performance and thermodynamic stability are required, for large-scale industrial applications

Methods

Results

Conclusion