Although traditional inorganic crystal thermoelectric materials have excellent thermoelectric properties, they have poor plasticity and machinability. This article has discovered the first inorganic amorphous material that has not only excellent plastic deformation properties, but also excellent electrical transport properties and thermoelectric properties. At the same time, the new material still has huge room for performance optimization, and it is suitable for thermoelectric materials, amorphous materials and even The field of semiconductor materials has important scientific significance.
Thermoelectric materials have received practical attention because they can realize the direct conversion between thermal energy and electrical energy through the movement of internal carriers, and have practical value in thermoelectric power generation and thermoelectric refrigeration. Although traditional inorganic crystal thermoelectric materials (such as Bi2Te3, GeTe, PbTe, etc.) have excellent thermoelectric properties, due to the strong ionic bonds and / or covalent bonds in the crystal structure, they usually show poor mechanical properties, especially Poor plasticity and machinability, easy to break under bending, tensile and compressive stress and cause device damage, limiting the practical application of thermoelectric materials. In recent years, the rapid development of wearable devices, microchips, etc. urgently requires self-powered batteries and micro-refrigeration devices based on thermoelectric conversion technology. At the same time, it also puts forward higher requirements on the mechanical properties of thermoelectric materials.
Professor Luo Jun of the School of Materials Science and Engineering of Shanghai University has conducted continuous and in-depth research on Ag2Te-based thermoelectric materials. Recently, he guided master students He Shiyang and Li Yongbo to discover an inorganic amorphous thermoelectric material Ag2 (Te, S) with excellent flexibility and thermoelectric properties. Relevant research results were published in Science Advances, Shanghai University as the first unit, Shanghai University of Materials Science and Engineering master students He Shiyang and Li Yongbo as co-first authors, Professor Luo Jun of Shanghai University, Professor Zhang Wenqing of Southern University of Science and Technology and Massachusetts Institute of Technology Professor Chen Gang is the co-corresponding author. This work was supported by projects such as the National Key R & D Program and the National Natural Science Foundation of China.
Paper link: https://advances.sciencemag.org/content/6/15/eaaz8423
Studies have shown that the Ag2 (Te, S) matrix is amorphous, and a small amount of crystallites are evenly dispersed in the amorphous matrix. The material not only has excellent plastic deformation properties such as tensile, compression and bending, but also has excellent electrical transport properties and thermoelectric properties. Ag2 (Te, S) 's excellent deformation properties and machinability are mainly derived from amorphous shear bands, and its excellent electrical transport properties are attributed to its ultra-high carrier mobility. In particular, the amorphous material exhibits extraordinary electrical properties, with a carrier concentration of up to 8.6 × 1018cm-3 at room temperature, a Hall mobility of 750cm2 · V-1 · s-1, and a power factor of up to 5.7 × 10-4W · M-1 · K-2, significantly better than conventional amorphous materials. Among them, the Hall mobility is two orders of magnitude higher than that of the amorphous materials that have been found, and the power factor is at least one order of magnitude higher.
At the same time, due to the structural disorder of the material itself, it leads to extremely low lattice thermal conductivity and thus exhibits excellent thermoelectric properties. The room temperature dimensionless thermoelectric figure of merit reaches 0.22, which is close to 0.70 at 300oC. With the temperature difference of 50K, the output power of the single-arm in-plane flexible device prepared by this material can reach 3.47 × 10-6W, and the output power density can reach 2.9W · m-2, which is better than most existing flexible thermoelectric devices. Considering that this new material still has a huge performance optimization space, it is expected to have important application value in flexible thermoelectric devices, sensors, and even more fields.
Ag2 (Te, S) is the first inorganic amorphous material with excellent flexibility and thermoelectric properties discovered so far. The discovery of this material has broken through the limitations of traditional narrow band gap semiconductor thermoelectric materials to a certain extent and expanded the inorganic thermoelectric materials. The versatility and research scope are of great scientific significance to thermoelectric materials, amorphous materials and even semiconductor materials.