Abstract EN:

The focus of this thesis work is the exploratory preparation of novel chalcogenides as potential thermoelectric materials and the analyses of their physical properties. A thermoelectric material is capable of converting heat to electricity or vice versa. Usually, narrow band gap semiconductors are good candidates for thermoelectric applications, because such materials have large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. In this work, two different systems were studied, intermetallic pseudo hollandite structures and layered CdI2 type structures. In the large family of pseudo hollandite systems, we mainly focused on thallium systems in which the solid solution TlxCr5Se8 and TlCr5Se8-xTex have been synthesized. In CdI2 structures, we focused our investigation on transition metal selenides for their rather semiconducting properties. Therefore we embarked on the systematic study of AgCrSe2, TiS2 and TiSe2. In addition, the effect on physical properties using different intercalated elements (Ag and Cu) in TiSe2 chalcogenides were studied. All these samples are prepared by the solid state reaction. The purity of the samples was confirmed by powder X-ray diffraction data, physical and thermal properties were measured on Spark Plasma Sintered (SPS) samples. Low thermal conductivity as well as competitive power factors was observed in these chalcogenides. The highest zT of 0. 54 is achieved in titanium dichalcogenides for the composition of Cu0. 05TiS1. 5Se0. 5 at 700K. Our results show that these structures are potential for future thermoelectric materials research.