Kondo semiconductors as a novel thermoelectric-cooling material

Among rare-earth-based compounds showing the Kondo effect, systems exhibiting a small energy gap in the heavy-electron band are referred to as Kondo semiconductors. We have measured thermoelectric properties of CeNiSn, CeRhSb, CeRhAs, YbB₁₂ and their substituted alloys. The thermopower of CeRhAs has a positive maximum of 130 μV/K at 40 K, while that of YbB₁₂ has a negative peak of -150 μV/K at 10 K. For both CeNiSn and CeRhSb, the electrical resistivity is less than 200 μΩcm and the thermal conductivity is about 50 mW/Kcm at 60 K. The figure of merit Z for CeRhAs and CeRhSb has the maximum value of 1.0×10^-3/K at 125 K and 2.2×10^-3/K at 13 K, respectively. Therefore, these compounds have high potential for a novel thermoelectric cooling material at low temperatures