The thermoelectric properties of the new compounds AgPb_mLaTe_(m+2) (m = 15, 18, 20, 25, 30, 35) were investigated in the temperature range of 300 to ～720 K and compared to those of AgPb_(18)MTe_(20) (M = Sb, Bi). All samples crystallize in the NaCl-type structure without noticeable secondary phase. The room-temperature electrical conductivities of the AgPb_mLaTe_(m+2) samples are > 1700 S/cm, which are higher than the Sb or Bi analog. The Seebeck coefficient in the AgPb_mLaTe_(m+2) samples ranges from -60μV/K at 300 K to - 160μV/K at 670 K and is much smaller than the Sb analog, but comparable to the Bi analog. A small Seebeck coefficient is consistent with a high electron concentration of the AgPb_mLaTe_(m+2) samples. The corresponding power factors (15-17 μW/(cm K~2) at ～670 K) of the AgPb_mLaTe_(m+2) samples are comparable to the Sb analog and higher than the Bi analog. The temperature dependent mobility of the La samples can be expressed through that of n-type degenerate PbTe samples. The derived room temperature lattice thermal conductivities of the AgPb_mLaTe_(m+2) samples are < 1.4 W/(m K), which are higher than that of the Sb analog (～0.8 W/(m K)) and are comparable to that of the Bi analog (～1.2 W/(m K)). A ZT of ～0.9 at ～670 K was achieved for the AgPb_(25)LaTe_(27).
展开▼
