Preparation and thermoelectric properties of A8IIB16IIIB30IV clathrate compounds

Abstract

Polycrystalline samples of clathrate compounds Ba8Ga16Si30, Ba8Ga16Ge30, Ba8Ga16Sn30, and Sr8Ga16Ge30 were prepared by direct melting and characterized using X-ray powder diffraction and differential thermal analysis. The Ge- and Si-based clathrates melt congruently, whereas Ba8Ga16Sn30 melts incongruently. At room temperature the Ge- and Si-based clathrates possess a moderate negative Seebeck coefficient and a high electron concentration in the range of 7×1020–9×1020 cm−3 while Ba8Ga16Sn30 exhibits substantially lower electron concentration of 2.2×1019 cm−3. The Seebeck coefficient and electrical resistivity were measured over the range 100–870 K. The temperature dependence of transport properties of the clathrates is typical for heavily doped semiconductors. The transport properties were analyzed using a standard semiconductor transport model. There is a good agreement between the assumed model and experimental temperature dependence of the Seebeck coefficient in the extrinsic conductivity range for all studied clathrates apart from Ba8Ga16Ge30. The calculated effective masses of the clathrates range from 0.9 to 3 of the free electron mass. The estimated ZT values are 0.7 for Ba8Ga16Ge30 at 700 K and 0.87 for Ba8Ga16Si30 at 870 K. The potential for thermoelectric applications of these materials is assessed.

Energetic Stability and Thermoelectric Property of Alkali-Metal-Encapsulated Type-I Silicon-Clathrate from First-Principles Calculation

“…Kuznetsov et al estimated the ZT of Ba 8 Ga 16 Si 30 to be 0.87 at 870 K, 13) and C. Candofi et al reported that a ZT of approximately 0.2 had been achieved at 600 K for Ba 8 Au xSi 46¹x , where x = 5.59.…”

NMR experiments and electronic structure calculations in type-I BaAlGe clathrates

“…[1][2][3][4][5] Clathrates consist of cages of silicon, germanium, or tin in a crystalline framework, with guest atoms located inside the cages. The type-I clathrates have the general formula M 8 X 46 , where M and X represent the guest atoms and framework atoms, respectively.…”

Functional Materials for Sustainable Energy Technologies: Four Case Studies

“…[56][57][58][59][60] ChemSusChem 2010, 3, 44 -58 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.chemsuschem.org trical conductivity typical of crystalline materials and, at the same time, a very low lattice thermal conductivity typical of an amorphous solid (so-called "electron-crystal, phonon-glass" materials). [62][63][64][65] The temperature dependence of ZT values of two n-type materials that belong to skutterudite (Yb 0.2 Co 4 Sb 12 ) and clathrate (Ba 8 Ga 16 Ge 30 ) families of inclusion compounds are presented in Figure 9.…”