Origin of low thermal conductivity in α-Mn: enhancing the ZT of YbAl3 and CoSb3 through Mn addition

The thermal conductivity of α-Mn is as low as Bi metal and is apparently due its complex crystal structure. The effect of Mn addition (doping and substitution) on the thermoelectric properties of rare earth intermetallics and skutterudites are explored. Although rare earth intermetallics such as YbAl₃, CePd₃ show high Seebeck coefficients and electrical conductivities resulting in very high power factors, the high inherent thermal conductivities make them not suitable for thermoelectrics. Mn doping in the YbAl₃ structure substantially lowers the lattice thermal conductivity without unduly decreasing the power factor thereby increasing the figure of merit (ZT). We have also substituted Mn for Co in CoSb₃ (without rattlers) resulting in the enhancement of ZT. Although modest enhancement of ZT is shown, this study indicates that the Mn could play an important role in the design strategy of high efficiency thermoelectrics.