High temperature thermoelectric efficiency in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Ba</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Ga</mml:mi><mml:mn>16</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Ge</mml:mi><mml:mn>30</mml:mn></mml:msub></mml:mrow></mml:math>

The high thermoelectric figure of merit $(zT)$ of ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ makes it one of the best $n$-type materials for thermoelectric power generation. Here, we describe the synthesis and characterization of a Czochralski pulled single crystal of ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ and polycrystalline disks. Measurements of the electrical conductivity, Hall effect, specific heat, coefficient of thermal expansion, thermal conductivity, and Seebeck coefficient were performed up to $1173\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and compared with literature results. Dilatometry measurements give a coefficient of thermal expansion of $16\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{0.3em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ up to $1175\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The trend in electronic properties with composition is typical of a heavily doped semiconductor. The maximum in the thermoelectric figure of merit is found at $1050\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with a value of 0.8. The correction of $zT$ due to thermal expansion is not significant compared to the measurement uncertainties involved. Comparing the thermoelectric efficiency of segmented materials, the effect of compatibility makes ${\mathrm{Ba}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ more efficient than the higher $zT$ $n$-type materials SiGe or skutterudite $\mathrm{Co}{\mathrm{Sb}}_{3}$.

Перевод пока недоступен