Nonstoichiometry and chemical purity effects in thermoelectric Ba8Ga16Ge30 clathrate
| Autor: | Galen D. Stucky, Bo B. Iversen, J. Daniel Bryan, Anders Bentien, Horia Metiu, Nick P. Blake, Rasmus D. Poulsen |
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| Rok vydání: | 2002 |
| Předmět: | |
| Zdroj: | Journal of Applied Physics. 92:7281-7290 |
| ISSN: | 1089-7550 0021-8979 |
| Popis: | Zone melting purification experiments have been carried out on the clathrate, Ba8Ga16Ge30. The impurities present have been identified and their approximate concentrations measured. Trace impurities were determined to be approximately 240 parts per million (ppm) in the most impure sample to 17 ppm in the most pure sample. The temperature-dependent Seebeck coefficient, thermal conductivity, and electrical conductivity are reported as a function of sample purity as well as the room-temperature Hall coefficient. Microprobe analysis suggests that the samples are nonstoichiometric with excess Ge relative to Ga, and there are indications of the presence of defects. Single-crystal x-ray investigations as well as synchrotron powder diffraction measurements support the presence of defects, but the x-ray data cannot accurately determine the relative amounts of Ga and Ge. Band-structure calculations in the generalized gradient approximation show that the measured Hall and Seebeck coefficients are consistent with a d... |
| Databáze: | OpenAIRE |
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