Thermoelectric Properties of Polycrystalline n-Type Pb5Bi6Se14

Chalcogenides are currently receiving attention due to their interesting thermoelectric properties that stem from their complex crystal structures and semiconducting properties. Here, we report on the synthesis and measurements of the transport properties in a broad temperature range (2-723 K) of polycrystalline n-type Pb5Bi6Se14, a member of the homologous series (PbSe)(5)(Bi2Se3)(3m) (m = 1), to assess its thermoelectric potential and to shed light on the basic mechanisms governing the low-temperature transport. The anisotropic crystal structure gives rise to transport properties that differ on samples measured parallel or perpendicular to the pressing direction. The measurements show that this compound exhibits semiconducting-like properties with thermopower values that reach 250 mu V K-1 at 723 K. The lattice thermal conductivity values are very low in the whole temperature range (similar to 0.5 W m(-1) K-1) and close to the theoretical minimum thermal conductivity estimated from sound velocities. Thanks to this remarkable property, a peak ZT of 0.5 is achieved at 720 K.