A new thermoelectric material:: CsBi4Te6

The highly anisotropic material CsBi4Te6 was prepared by the reaction of Cs/Bi2Te3 around 600 degreesC. The compound crystallizes in the monoclinic space group C2/m with a = 51.9205(8) Angstrom, b = 4.4025(1) Angstrom, c = 14.5118(3) Angstrom, beta = 101.480(1)degrees, V = 3250.75(11) Angstrom(3), and Z = 8. The final R values are R-1 = 0.0585 and wR(2) = 0.1127 for all data. The compound has a 2-D structure composed of NaCl-type [Bi4Te6] anionic layers and Cs+ ions residing between the layers. The [Bi4Te6] layers are interconnected by Bi-Bi bonds at a distance of 3.2383(10) Angstrom. This material is a narrow gap semiconductor. Optimization studies on the thermoelectric properties with a variety of doping agents show that the electrical properties of CsBi4Te6 can be tuned to yield an optimized thermoelectric material which is promising for low-temperature applications. Sbl(3) doping resulted in p-type behavior and a maximum power factor of 51.5 muW/cm(.)K(2) at 184 K and the corresponding ZT of 0.82 at 225 K. The highest power factor of 59.8 muW/cm(.)K(2) at 151 K was obtained from 0.06% Sb-doped material. We report here the synthesis, physicochemical properties, doping characteristics, charge-transport properties, and thermal conductivity. Also presented are studies on n-type CsBi4Te6 and comparisons to those of p-type.