Charge-Compensated Compound Defects in Ga-containing Thermoelectric Skutterudites
Charge-Compensated Compound Defects in Ga-containing Thermoelectric Skutterudites
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含镓热电方钴矿中的电荷补偿化合物缺陷
DOI：
10.1002/adfm.201202571
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发表时间：
2013-07-05
影响因子：
19
通讯作者：
Snyder, G. Jeffrey
中科院分区：
文献类型：
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作者：
Qiu, Yuting;Xi, Lili;Snyder, G. Jeffrey
重掺杂通过引入杂质态将本征半导体变成金属导体。然而，具有晶格空隙的热电方钴矿CoSb 3中的Ga杂质提供了相反的示例。由于单个Ga杂质的双位占位，形成电荷补偿的化合物缺陷。通过第一性原理计算和实验相结合，我们发现Ga原子占据了CoSb 3中的空位和Sb位，并相互耦合。来自填充空隙的Ga（Ga-VF）的捐赠电子使来自Sb取代的Ga（Ga-Sb）的悬挂键饱和。Ga杂质作为化合物缺陷的稳定化使方钴矿相的稳定区域向Ga 0.15Co 4Sb 11.95方向扩展，而在三元相图的其他方向上的固溶区域则小得多。提出了Ga-Co-Sb三元相图。这种补偿的缺陷复合物导致在CoSb 3中具有重Ga掺杂的几乎本征的半导体和大大降低的晶格热导率（（L）），这也可以归因于双位占据者Ga杂质对低频和高频晶格声子的有效散射。这样的系统保持低载流子浓度并因此保持高热功率，并且在Ga掺杂含量低至每Co 4Sb 12 0.1和低载流子浓度为10（19）cm（-3）量级时热电优值迅速增加至0.7。
Heavy doping changes an intrinsic semiconductor into a metallic conductor by the introduction of impurity states. However, Ga impurities in thermoelectric skutterudite CoSb3 with lattice voids provides an example to the contrary. Because of dual-site occupancy of the single Ga impurity charge-compensated compound defects are formed. By combining first-principle calculations and experiments, we show that Ga atoms occupy both the void and Sb sites in CoSb3 and couple with each other. The donated electrons from the void-filling Ga (Ga-VF) saturate the dangling bonds from the Sb-substitutional Ga (Ga-Sb). The stabilization of Ga impurity as a compound defect extends the region of skutterudite phase stability toward Ga0.15Co4Sb11.95 whereas the solid-solution region in other directions of the ternary phase diagram is much smaller. A proposed ternary phase diagram for Ga-Co-Sb is given. This compensated defect complex leads to a nearly intrinsic semiconductor with heavy Ga doping in CoSb3 and a much reduced lattice thermal conductivity ((L)) which can also be attributed to the effective scattering of both the low- and high-frequency lattice phonons by the dual-site occupant Ga impurities. Such a system maintains a low carrier concentration and therefore high thermopower, and the thermoelectric figure of merit quickly increases to 0.7 at a Ga doping content as low as 0.1 per Co4Sb12 and low carrier concentrations on the order of 10(19) cm(-3).