Effect of Bi Substitution on Thermoelectric Properties of SbSe2-based Layered Compounds NdO$_{0.8}$F$_{0.2}$Sb$_{1-x}$Bi$_x$Se$_2$

Although SbSe2-based layered compounds have been predicted to be high-performance thermoelectric materials and topological materials, most of these compounds obtained experimentally have been insulators so far. Here, we present the effect of Bi substitution on the thermoelectric properties of SbSe2-based layered compounds NdO0.8F0.2Sb1-xBixSe2 (x = 0-0.4). The room temperature electrical resistivity is decreased to 8.0 * 10^-5 ohmm for x = 0.4. The electrical power factor is calculated to be 1.4 * 10^-4 W/mK^2 at 660 K, which is in reasonable agreement with combined Jonker and Ioffe analysis. The room-temperature lattice thermal conductivity of less than 1 W/mK is almost independent of x, in contrast to the point-defect scattering model for conventional alloys. The present work provides an avenue for exploring SbSe2-based insulating and BiSe2-based conducting systems.