We investigated the thermoelectric properties of Ba
8Al
16Si
30 clathrate samples prepared by combining arc melting and spark plasma sintering methods under two different arc melting conditions. The x-ray diffraction, scanning electron microscopy, and energy dispersive analysis of x-ray studies indicate that Al composition is close to 15, which is higher than that of a single crystal reported, for both arc melting conditions. The carrier concentration of samples decreases to about 1×10
21 cm
-3, which is lower than reported values so far in Ba
8Al
16Si
30 system. The Seebeck coefficient and the electrical conductivity alter slightly with the arc melting condition due to the slight difference in the carrier concentration. The lattice thermal conductivity (RT) is as low as about 1.3 Wm
-1K
-1, which is comparable to Bi
2Te
3-based bulk alloy, independently of the arc melting condition. The thermoelectric figure of merit
ZT is about 0.4 at 900 K. An estimation indicates that
ZT reaches 0.8 (1200 K) at the optimum carrier concentration of about 3×10
20 cm
-3 in Ba
8Al
16Si
30 system.
抄録全体を表示