Researchers from the Institute of Metals have discovered a new material with both low thermal conductivity and high rigidity

Researchers such as Researcher Li Bing and Researcher Zhang Zhidong from the Institute of Metal Research and collaborators discovered that copper diphosphide crystals have both high sound velocity and low thermal conductivity, which are distinct from the low sound velocity and softer characteristics of conventional low thermal conductivity materials.
Contrast
.
The results of this study were published in Nature Communications on October 15
.
? High thermal conductivity materials have important applications in cooling system heat dissipation, electronic components thermal management, etc.
, while low thermal conductivity materials are often used to build an adiabatic environment
.
Electrons, magnons, and lattices can all conduct heat.
As the most basic heat-conducting carrier of solid materials, the greater the speed of sound, the greater the thermal conductivity
.
? The study found that the layered crystal material copper diphosphide has a sound velocity similar to that of the classic semiconductor material gallium arsenide, but the thermal conductivity is one order of magnitude lower
.
In response to this abnormal behavior, researchers used inelastic neutron scattering technology to systematically study the lattice dynamics of the crystal, revealing from the atomic level that this abnormal behavior originated from the weakly bonded local vibration mode of copper atom pairs (rattling Vibration mode)
.
In this study, researchers presented a complete picture of lattice dynamics, which provided a guarantee for a deep understanding of the abnormal heat conduction behavior of the material
.
The discovery of this new material is expected to be applied in occasions with good rigidity and thermal insulation at the same time
.
? Researchers from the Institute of Metals used the POWGEN diffractometer of the Spallation Neutron Source (SNS) of the Oak Ridge National Laboratory in the United States to study the crystal structure of the material
.
Copper diphosphide has a layered structure, and a network of phosphorus atoms and copper atomic layers are alternately arranged
.
In particular, copper atoms form an isolated pair of atoms, and the distance between the pairs is relatively long
.
Using the BL04B2 spectrometer of the Japanese high-energy synchrotron radiation facility (SPring-8), the pair distribution function of the material is obtained.
The analysis shows that there is no atomic disorder in the system, which eliminates the scattering effect of atomic disorder on phonons.

.
Researchers have grown a large single crystal, combined use of the Australian Nuclear Science and Technology Organization (ANSTO) Pelican and thermal neutron triaxial spectrometer Taipan, selected three cloths (200), (022) and (111) In the Liyuan area, the lattice dynamics of the material has been systematically studied, and the dispersion relationship obtained by the experiment is completely consistent with the first-principles calculation results
.
In terms of lattice dynamics, the copper atom pair presents a weakly bonded local vibration mode
.
The frequency of this mode is about 11 meV at low temperature.
As the temperature rises, it softens sharply, showing strong anharmonicity
.
In terms of the dispersion relationship, anti-crossing features are found, indicating that this weakly bonded local vibration mode strongly scatters longitudinal acoustic phonons
.
Because acoustic phonons are the main participants in heat conduction, especially longitudinal acoustic phonons
.
Therefore, the scattering of longitudinal acoustic phonons by this mode leads to a lower phonon lifetime, which offsets the contribution of high sound velocity to the thermal conductivity, which is the direct cause of the low thermal conductivity of the crystal
.