Hoque Md Shafkat Bin, Hoglund Eric R, Zhao Boyang, Bao De-Liang, Zhou Hao, Thakur Sandip, Osei-Agyemang Eric, Hattar Khalid, Scott Ethan A, Surendran Mythili, Tomko John A, Gaskins John T, Aryana Kiumars, Makarem Sara, Alwen Adie, Hodge Andrea M, Balasubramanian Ganesh, Giri Ashutosh, Feng Tianli, Hachtel Jordan A, Ravichandran Jayakanth, Pantelides Sokrates T, Hopkins Patrick E
Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, USA.
Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, USA.
Nat Commun. 2025 Jul 2;16(1):6104. doi: 10.1038/s41467-025-61078-5.
Insulating materials featuring ultralow thermal conductivity for diverse applications also require robust mechanical properties. Conventional thinking, however, which correlates strong bonding with high atomic-vibration-mediated heat conduction, led to diverse weakly bonded materials that feature ultralow thermal conductivity and low elastic moduli. One must, therefore, search for strongly-bonded single crystals in which heat transport is impeded by other means. Here, we report intrinsic, glass-like, ultralow thermal conductivity and ultrahigh elastic-modulus/thermal-conductivity ratio in single-crystalline Ruddlesden-Popper BaZrS, n = 2, 3, which are derivatives of BaZrS. Their key features are strong anharmonicity and intra-unit-cell rock-salt blocks. The latter produce strongly bonded intrinsic superlattices, impeding heat conduction by broadband reduction of phonon velocities and mean free paths and concomitant strong phonon localization. The present study initiates a paradigm of "mechanically stiff phonon glasses".
用于各种应用的具有超低热导率的绝缘材料也需要强大的机械性能。然而，传统观念将强键合与由高原子振动介导的热传导联系起来，导致了各种具有超低热导率和低弹性模量的弱键合材料。因此，人们必须寻找通过其他方式阻碍热传输的强键合单晶。在这里，我们报道了单晶Ruddlesden-Popper BaZrS（n = 2, 3，它们是BaZrS的衍生物）中固有的、类似玻璃的超低热导率和超高弹性模量/热导率比。它们的关键特征是强非谐性和晶胞内的岩盐块。后者产生强键合的本征超晶格，通过声子速度和平均自由程的宽带降低以及伴随的强声子局域化来阻碍热传导。本研究开创了“机械刚性声子玻璃”的范例。
