论文标题
多载全赫斯勒化合物的高热电性能和缺陷能量学
High Thermoelectric Performance and Defect Energetics of Multi-pocketed Full-Heusler Compounds
论文作者
论文摘要
我们报告了全赫斯勒化合物SR $ _ {2} $ biau和sr $ _ {2} $ sbau的第一原理密度功能性研究。我们的结果表明，在各种温度上，超高的内在体积热电性能是物理上可能的，并且指出存在多重变性和高度分散的载体口袋是实现它的关键因素。 Sr $ _ {2} $ biau具有十个能量与能量的低效能大型口袋（沿$γ-x $六个，$ l $的四个），预计将提供$ n $ n $ -n $ type $ zt = 0.4-4.9 $ at $ t = 100-700 $ 〜k。与先前研究的BA $ _ {2} $ BIAU化合物的比较表明，Sr $ _ {2} $ _ {2} $ biau的附加$ l $ pockets显着将其低温功率因数提高到最大值$ 12 $ 〜mw〜mw〜mw〜m $^m $^{-1} $^{ - 1} $ 〜k $^k $^{ - 2} $^{ - 2} $ near $ near $ n $ the $ t $ t = 300 $ t = 300 $ t = 300。但是，在高温下，Sr $ _ {2} $ biau的功率因数下降到Ba $ _ {2} $ biau的功率因数以下，因为$ l $状态较大，并且会通过声音变形较重，并且与较轻的$γ-X $状态相对于受极性散射限制的较轻的$γ-X $。 Sr $ _ {2} $ SBAU预计将提供较低的$ n $ type $ Zt = 3.4 $ at $ t = 750 $ 〜k，这是由于$ L $和$γ-X $载体袋之间的明显未对准，通常较重的散射，且晶状体导热率较高。负责低晶格导热系数的软声学模式，也增加了助母子化合物的振动熵和高温稳定性，这表明它们的实验合成可能是可行的。发现主要的内在缺陷是AU空缺，它将费米水平推向传导带，并支持$ n $的兴趣。
We report first-principles density-functional study of electron-phonon interactions and thermoelectric transport properties of full-Heusler compounds Sr$_{2}$BiAu and Sr$_{2}$SbAu. Our results show that ultrahigh intrinsic bulk thermoelectric performance across a wide range of temperatures is physically possible and point to the presence of multiply degenerate and highly dispersive carrier pockets as the key factor for achieving it. Sr$_{2}$BiAu, which features ten energy-aligned low effective mass pockets (six along $Γ-X$ and four at $L$), is predicted to deliver $n$-type $zT=0.4-4.9$ at $T=100-700$~K. Comparison with the previously investigated Ba$_{2}$BiAu compound shows that the additional $L$-pockets in Sr$_{2}$BiAu significantly increase its low-temperature power factor to a maximum value of $12$~mW~m$^{-1}$~K$^{-2}$ near $T=300$~K. However, at high temperatures the power factor of Sr$_{2}$BiAu drops below that of Ba$_{2}$BiAu because the $L$ states are heavier and subject to strong scattering by phonon deformation as opposed to the lighter $Γ-X$ states that are limited by polar-optical scattering. Sr$_{2}$SbAu is predicted to deliver lower $n$-type of $zT=3.4$ at $T=750$~K due to appreciable misalignment between the $L$ and $Γ-X$ carrier pockets, generally heavier scattering, and slightly higher lattice thermal conductivity. Soft acoustic modes, responsible for low lattice thermal conductivity, also increase vibrational entropies and high-temperature stability of the Heusler compounds, suggesting that their experimental synthesis may be feasible. The dominant intrinsic defects are found to be Au vacancies, which drive the Fermi level towards the conduction band and work in favor of $n$-doping.
