Thermal Stability and Phase Purity in Polycrystalline Ba8GaxGe46−x
Polycrystalline Ba8GaxGe46−x exhibits promising thermoelectric performance with the figure of merit ZT close to that of single crystals. Polycrystalline Ba8GaxGe46−x is promising for applications, but reproducibility and thermal stability of thermoelectric properties need to be demonstrated. Polycrystalline samples of Ba8+dGaxGe46−x-type clathrates (15.0 ≤ x ≤ 16.8 with varied nominal Ga content and d = 0 or 0.2) were prepared by direct reaction of the elements, followed by ball milling and hot pressing. Trace Ge impurity was observed (<1.0 wt.%) depending on the synthesis method. The electrical resistivity was stable in measurements up to 1000 K, regardless of Ge impurity. However, measurements to 1050 K resulted in irreversible increase in carrier concentration while the carrier mobility remained unchanged.
KeywordsClathrate electrical resistivity carrier concentration Ba8Ga16Ge30 thermoelectricity
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- 10.H. Anno, M. Hokazono, M. Kawamura, J. Nagao, and K. Matsubara, Proceedings of the 21st International Conference on Thermoelectrics, 2002, p. 77.Google Scholar
- 15.J.A. McCormack and J.P. Fleurial, Materials Research Society Symposium Proceedings, 1991, p. 135.Google Scholar