Flapping vibrations contributed to heat insulation in Cs_(2)ZnI_(4)OA
Shear modulus is commonly lower than its elastic counterpart in solids,leading to our experience that in the elastic region,it is usually much easier to shear than to compress/stretch a solid.Scientifically,this implies an easier change in molecular bonding angle than bonding length,further corresponding to the normally observed phenomenon that the propagation of longitudinal lattice vibrations is faster than that of shear ones.Populating the easier vibrations of flapping bond angles fundamentally opens an opportunity to insulate heat conduction in solids,since this type of vibration ensures slow propagation and low energy/frequency,leading to a low thermal conductivity.Here we demonstrate that single-crystalline orthorhombic Cs_(2)ZnI_(4),with two sets of extremely low-frequency flapping vibrations in the crystallographic planes of ac(0.4 THz)and bc(0.5 THz),respectively,exhibits extraordinarily low thermal conductivities of 0.11 W m^(-1)K^(-1)along the c direction and of 0.16 W m^(-1)K^(-1)along the b direction at room temperature,as compared to∼0.2 W m^(-1)K^(-1)in existing heat insulators in the dense form.The strategy and material developed in this work are believed to enrich the advancements of heat insulation technology.
Linjie Wu;Pengfei Nan;Long Yang;Zhiwei Chen;Changyuan Li;Qingyu Bai;Hongzheng Wang;Sui Ting Tai;Chen Wang;Binghui Ge;Yue Chen;Jun Luo;Yanzhong Pei
Interdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInstitutes of Physical Science and Information Technology,Anhui University,Hefei 230601,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInstitutes of Physical Science and Information Technology,Anhui University,Hefei 230601,ChinaDepartment of Mechanical Engineering,The University of Hong Kong,Hong Kong 999077,ChinaDepartment of Mechanical Engineering,The University of Hong Kong,Hong Kong 999077,ChinaInstitutes of Physical Science and Information Technology,Anhui University,Hefei 230601,ChinaDepartment of Mechanical Engineering,The University of Hong Kong,Hong Kong 999077,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,ChinaInterdisciplinary Materials Research Center,School of Materials Science and Engineering,Tongji University,Shanghai 201804,China
化学化工
flapping vibrationssingle crystalheat insulation
《National Science Review》 2026 (12)
P.193-201,9
supported by the National Key Research and Development Program of China(2022YFA1203600)the National Natural Science Foundation of China(T2125008,52532009,92263108,92163203,52302193 and 52102292)the Shanghai Rising-Star Program(23QA1409300)the Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-07-E00096)the Fundamental Research Funds for the Central Universities.Research conducted at the Center for High-Energy X-ray Science(CHEXS)was supported by the National Science Foundation(BIO,ENG,and MPS Directorates)under award DMR-182907.
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