ICT2014 Abstracts

Recently, research in copper based quaternary chalcogenide materials has focused on the study of thermoelectric properties due to the complexity in the crystal structure. In the present work, stoichiometric quaternary chalcogenide compounds Cu_2+xCd_1-xGeSe₄ (x = 0, 0.025, 0.05, 0.075, 0.1) were prepared by solid state synthesis. Powder X-ray diffraction patterns of all the samples showed a tetra­gonal crystal structure with the space group I-42m of the main phase, whereas the samples withx = 0 and x = 0.025 revealed the presence of an orthorhombic phase in addition to the main phase confirmed by Rietveld analysis. The elemental composition of all the samples characterized by Electron Probe Micro Analyzer showed a slight deviation from the nominal composition. The transport properties were measured in the temperature range of 300 K – 723 K. The electrical conductivity of all the samples increased with increasing Cu content due to the enhancement of the hole concentration caused by the substitution of Cd (divalent) by Cu (monovalent). The positive Seebeck coefficient of all the samples in the entire temperature ranges indicates that holes are the majority carriers. The Seebeck coefficient of all the samples decreased with increasing Cu content and showed a reverse trend to the electrical conductivity. The total thermal conductivity of all the samples decreased with increasing temperature which was dominated by the lattice contribution. The maximum figure of merit ZT = 0.42 at 723 K is obtained for the compound Cu_2.1Cd_0.9GeSe₄.