Semiconducting nature and thermal transport studies of ZrTe3

We report electrical and thermal transport properties of polycrystalline ZrTe3. The polycrystalline sample shows semiconducting behavior in contrast to the established semi-metallic character of the compound. However the charge density wave (CDW) transition remains intact and its clear signatures are observed in thermal conductivity and Seebeck coefficient, in the wide temperature range 50 - 100 K. The thermal conductivity points to additional scattering from the low frequency phonons (phonon softening) in the vicinity of CDW transition. The transport in the polycrystalline compounds is governed by smaller size polarons in the variable range hopping (VRH) region. However, the increasing disorder in polycrystalline compounds suppresses the CDW transition. The VRH behavior is also observed in the Seebeck coefficient data in the similar temperature range. The Seebeck coefficient suggests a competition between the charge carriers (electrons and hole).