A research team from the Interdisciplinary Materials Research Center iMAT at Aarhus University in Denmark has discovered that the crystalline material AgGaGe₃Se₈ exhibits unusually low thermal conductivity. The material displays glass-like behavior in heat transport and has become one of the crystalline solids with the lowest known thermal conductivity.
Research data show that the thermal conductivity of AgGaGe₃Se₈ at room temperature is only 0.2W/m·K, approximately one-third that of water and one-fifth that of typical quartz glass. This crystalline material, composed of silver, gallium, germanium, and selenium, was previously studied mainly for its optical properties. This is the first systematic measurement of its thermal transport properties.
Using synchrotron X-ray scattering data from the Spring-8 facility in Japan, the researchers found that the special behavior of silver atoms in the material is the key factor behind the low thermal conductivity. Researchers at Aarhus University stated: "Silver atoms are not fixed within the crystal lattice but exist in a loosely bound state and move irregularly." This atomic-level disorder disrupts the normal propagation of phonons, significantly reducing thermal conduction efficiency.
This glass-like heat transport behavior remains stable over a wide temperature range from 2K to 700K (−271°C to 400°C), which is very rare in crystalline materials. Although the material is currently difficult to apply directly due to its poor electrical conductivity and the presence of expensive germanium, this study provides important insights for material design.
The research results have been published in the journal Science Advances. The discovery has guiding significance for energy technologies such as thermoelectric conversion and thermal barrier coatings, and provides a theoretical foundation for developing new thermal management materials. The researchers stated that understanding how specific structural features affect heat transport will help design new functional materials with customized thermal conductivity properties.
