Incipient Ferroelectricity in Thermoelectric Lead Telluride

PbTe, is the parent compound of currently the most important thermoelectric (TE) materials in applications just above room temperature [1]. It has an anomalously low thermal conductivity resulting in a rather high TE figure of merit. Our neutron total scattering and atomic pair distribution function analysis shows the existence of a novel paraelectric state at and above room temperature. However, on cooling the structural dipoles do not order, but disappear resulting in an undistorted rock-salt ground-state. We suggest that new thermoelectrics should be sought among materials that, like PbTe [2], are close to a ferroelectric instability.\\[4pt] [1] Z.H. Dughaish, Physica B v.322, pp205 (2002).\\[0pt] [2] E.S. Bozin et al, Science (to be published).