Thermoelectric Properties of CoSb 3 -based Skutterudite Compounds
- PDF / 193,942 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 97 Downloads / 225 Views
1267-DD03-02
Thermoelectric Properties of CoSb3-based Skutterudite Compounds. Adul Harnwunggmoung1,2, Ken Kurosaki1, Hiroaki Muta1, and Shinsuke Yamanaka1,3 1
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan 2 Faculty of Science and Technology, Rajamangala University of Technology Suvarnabhumi, 60 Moo 3, Asia Road, Huntra Phranakhon Si Ayutthaya 13000, Thailand 3 Research Institute of Nuclear Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan ABSTRACT CoSb3 is known as a skutterudite compound that could exhibit high thermoelectric figure of merit. However, the thermal conductivity of CoSb3 is relatively high. In order to enhance the thermoelectric performance of this compound, we tried to reduce the thermal conductivity of CoSb3 by substitution of Rh for Co and by Tl-filling into the voids. The polycrystalline samples of (Co,Rh)Sb3 and Tl-filled CoSb3 were prepared and the thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured in the temperature range from room temperature to 750 K. The Rh substitution for Co reduced the lattice thermal conductivity, due to the alloy scattering effect. The minimum value of the lattice thermal conductivity was 4 Wm-1K-1 at 750 K obtained for (Co0.7Rh0.3)Sb3. Also the lattice thermal conductivity rapidly decreased with increasing the Tl-filling ratio. Tl0.25Co4Sb12 exhibited the best ZT values; the maximum ZT was 0.9 obtained at 600 K. INTRODUCTION Thermoelectric materials are capable of converting waste heat to usable electricity. The effectiveness of a material for thermoelectric applications is determined by the dimensionless figure of merit, ZT = S2T/ρ/κ, where S is the Seebeck coefficient, ρ is the electrical resistivity, κ is the thermal conductivity, and T is the absolute temperature[1,2]. The ZT value of the materials used in current devices is approximately 1. In recent years, several classes of bulk materials[3,4] with high ZT have been discovered, including filled skutterudites[5-7]. Skutterudite compounds have the composition MX3 where M is a metal atom such as Co, Rh, or Ir and X represents a pnicogen atom such as P, As, and Sb. These compounds are bodycentered cubic with 34 atoms in the unit cell and space group Im3. There are two voids per unit cell in the structure. When the third atom incorporates into the void, the formula of the compounds turns out to be RM4X12, where R is most often a rare-earth element, called filledskutterudite structure[8]. The R atom is bonded weakly with the other atoms and rattles. Therefore, the introduction of R atoms into the voids of the skutterudites is an effective method of reducing the lattice thermal conductivity such as thallium-filled skutterudites[9]. In addition to the rattling effect, the lattice thermal conductivity could be reduced by the alloy scattering effect. The alloying can reduce the lattice thermal conductivity by the point defect phonon scattering while giving little influence on the ele
Data Loading...
