熱導率是材料最基本的物理性能之一,更是熱電能量轉換等材料的核心參數,因此快速判斷和預測材料的熱導率具有重要的科學意義和應用價值。在半導體材料中,晶格熱導率(L)通常佔主導,其數值大小取決於從原子/晶格到晶粒等幾乎全尺度的結構特徵和多種物理作用過程。材料基因工程基於性能判據和高通量計算,為特定性能材料的篩選提供了新的理念和方法。然而,晶格熱導率涉及多種物理機制和過程,難以提出一種兼顧效率(簡潔直觀)與準確性(豐富內涵)的篩選判據,尤其是對結構複雜、種類繁多的新型化合物。
日前,中國科學院上海矽酸研究所史迅、陳立東研究員聯合上海大學楊炯教授、上海交通大學魏天然助理教授等,以近年來熱電、光電等領域備受關注的銅/銀基三元硫屬化合物為示範,基於73種材料的晶格熱導率數據和晶體學信息,提出了快速預測材料晶格熱導率的直觀判據——陰陽離子數失配度δ = (Ncation-Nanion)/Nanion)。作者以具有較大離子數失配的Cu4Sn7S16(d = -0.3125)複雜結構化合物為例,精細解析了材料的晶體結構和晶格振動模式,分析了低溫熱輸運性質,建立了表觀陰陽離子數失配與微觀結構畸變、晶胞複雜化以及熱導率的關聯,系統闡釋了該判據的科學內涵。接下來,作者基於此判據預測了一種結構未知的低熱導新材料Cu2Sn4S9(d = -0.33),並通過實驗進行了驗證。這一簡潔直觀的離子數失配判據很好地解釋了實驗現象,篩選出了新的低晶格熱導化合物,有望進一步推廣到其他複雜化合物體系,為低熱導化合物的快速篩選提供指導。
該文近期發表於npj Computational Materials 6: 81 (2020),英文標題與摘要如下,點擊https://www.nature.com/articles/s41524-020-00355-x可以自由獲取論文PDF。
圖2陰陽離子數失配對熱輸運的影響示意圖
Figure 2. Effects of δ on thermal transport.
Number mismatch between cations and anions as an indicator for low lattice thermal conductivity in chalcogenides
Tingting Deng,|| Tian-Ran Wei,|| Hui Huang, Qingfeng Song, Kunpeng Zhao, Pengfei Qiu, Jiong Yang,* Lidong Chen, Xun Shi*
Thermal conductivity is one of the most fundamental properties of materials with the value being determined by nearly all-scale structural features and multiple physical processes. Rapidly judging material’s thermal conductivity is extremely important but challenging for the applications. The material genome paradigm offers a revolutionary way to efficiently screen and discover materials with designed properties by using accessible indicators. But such a performance indicator for thermal conductivity is quite difficult to propose due to the existence of multiple mechanisms and processes, especially for the materials with complex structures such as chalcogenides. In this study, the number mismatch between cations and anions is proposed as a practical performance indicator for lattice thermal conductivity in complex copper and silver chalcogenides, which can be used to explain the observed experimental data and find new low thermal conductivity materials. Such a number mismatch brings about rich phenomena to affect thermal conductivity including the complication of the unit cell and the creation of chemical hierarchy, point defects, rattling modes and lone pair electrons. It is expected that this rich-connotation performance indicator can be also extended to other complex materials to discover designed thermal conductivities.