Applied Physics Letters · 1998 · 949 citations · 11 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsSemiconductor MaterialsSolid State PhysicsHeat ConductionSemiconducting MaterialsThermal Properties Of MaterialsThermal Properties Of SemiconductorsThermoelectric MaterialsWide Band Gap SemiconductorsClathratesSeebeck CoefficientThermal ConductivityThermoelectric CoolingThermoelectric Figure Of MeritThermoelectric PropertiesThermoelectric TransportThermoelectric Transport Coefficients
Transport properties of polycrystalline Ge clathrates with general composition Sr8Ga16Ge30 are reported in the temperature range 5 K⩽T⩽300 K. These compounds exhibit N-type semiconducting behavior with relatively high Seebeck coefficients and electrical conductivity, and room temperature carrier concentrations in the range of 1017–1018 cm−3. The thermal conductivity is more than an order of magnitude smaller than that of crystalline germanium and has a glasslike temperature dependence. The resulting thermoelectric figure of merit, ZT, at room temperature for the present samples is 14 that of Bi2Te3 alloys currently used in devices for thermoelectric cooling. Extrapolating our measurements to above room temperature, we estimate that ZT>1 at T>700 K, thus exceeding that of most known materials.
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