ICT2014 Abstracts

Thermoelectric materials can harvest waste heat and generate electricity, and therefore, enhance energy use ratio. They can also serve as solid state cooler extracting heat with electricity. Crystalline materials with type I clathrate structure have drawn intense research interests for the potential in thermoelectric applications. Type I clathrates are often described as “PGEC” materials with their vibrating guest atoms coupling phonon, and decreasing the thermal conductivity. Alkali metal containing silicon based type I clathrates A₈Ga₈Si₃₈ (A = K, Rb, Cs) were synthesized through solid state reactions. K₈Al₈Si₃₈ was synthesized through ball milled hydride route and studied as comparison. The polycrystalline samples were confirmed to be phase pure type I clathrates by powder XRD. Their unit cell parameters were determined with unit cell refinement. The structure details were studied by X-ray crystallography and synchrotron X-ray diffraction. Samples were consolidated by SPSS (Spark Plasma Sintering System) at 625C. The thermoelectric properties of sintered samples were investigated with PPMS (Physical Property Measurement System) at low temperature. The samples all possess low thermal conductivity (0.5 W/Km ~ 1.6 W/Km). K₈Al₈Si₃₈ and K₈Ga₈Si₃₈ were confirmed to be n type semiconductor, while Rb₈Ga₈Si₃₈ and Cs₈Ga₈Si₃₈ were confirmed to be p type semiconductor.