Filling Yb atoms into the nanovoid of skutterudites has been long the main strategy to achieve high thermoelectric performance. However, both the ZT and the Yb actual total filling fraction (ATFF) show great discrepancies among the literature. The underlying mechanisms behind such discrepancy still keep mysterious. Here, we theoretically and experimentally study the solid solution and phase transformation in the un-filled, single-filled, and multiple-filled skutterudites from a kinetics perspective. The ZT and ATFF discrepancies are thus explained by the complex reaction process. Our density functional theory calculations indicate that an extraordinarily large energy barrier exists in the solid solution process of Yb atoms in CoSb₃.The introduction of other filling atoms can further reduce the Yb diffusion rate, putting off the overall reaction process. As the reaction progresses, the ATFF first increases sharply and finally keeps constant, representing the complex phase transition behaviors from non-equilibrium microstructures to equilibrium microstructures. Through optimizing the synthesis route, we successfully promote the reaction process to the ultimate limit in the Yb_0.3Ca_0.1Al_0.1Ga_0.1In_0.1Co_3.75Fe_0.25Sb₁₂ sample. A remarkable theoretical conversion efficiency of 14.12% is achieved, exhibiting excellent stability and reproducibility as expected. Our results provide an intrinsic understanding of chemical doping from materials science essentials, which is applicable for designing other high-performance functional materials.

将Yb原子填充到方钴矿的纳米空隙中一直是实现高热电性能的主要策略。但是，ZT和Yb实际总填充率（ATFF）在文献之间显示出很大的差异。这种差异背后的潜在机制仍然神秘。在这里，我们从动力学的角度理论上和实验上研究了未填充，单填充和多填充的方钴矿中的固溶体和相变。因此，ZT和ATFF的差异可以通过复杂的反应过程来解释。我们的密度泛函理论计算表明，CoSb ₃中Yb原子的固溶过程中存在非常大的能垒引入其他填充原子可以进一步降低Yb扩散速率，推迟整个反应过程。随着反应的进行，ATFF首先急剧增加，最后保持恒定，代表了从非平衡微结构到平衡微结构的复杂相变行为。通过优化合成路线，我们成功地将反应过程提高到了Yb _0.3 Ca _0.1 Al _0.1 Ga _0.1 In _0.1 Co _3.75 Fe _0.25 Sb _12的极限样品。达到了惊人的14.12％的理论转化效率，具有预期的优异稳定性和可重复性。我们的结果从材料科学的本质上提供了对化学掺杂的内在理解，可用于设计其他高性能功能材料。