Researchers at the Beijing High Voltage Scientific Research Center and Chinese and American scientists have used compression lattices to induce topological phase transitions, and the thermoelectric figure of merit of the chromium-doped lead-selenium system has been increased to 1.7 at room temperature, which is much higher than the generally recognized highest room temperature value. This discovery not only provides a new method to improve the figure of merit of thermoelectricity, but also brings dawn for the future technical application of thermoelectric materials at room temperature, especially to solve the heating problems of microelectronic devices related to mobile phones. Related achievements were published online in "Nature-Materials" on October 7.
Thermoelectric material is a kind of functional material that directly converts thermal energy and electrical energy. The conversion efficiency is determined by the thermoelectric figure of merit. The study found that once the value is greater than 3, the conversion efficiency of thermoelectric devices may exceed 30%, which is almost equivalent to the conversion efficiency of traditional fuels such as coal and petroleum. Historically, the highest thermoelectric figure of merit at room temperature has been hovering around 1 for a long time, and to solve the heat problem of microelectronic devices such as mobile phones, there is an urgent need to significantly improve the thermoelectric figure of merit at room temperature.
The researchers chose 1% chromium-doped lead selenide as the research object, and obtained the shape of the peak-like thermoelectric figure of merit with pressure changes through the self-developed high-pressure thermoelectric property comprehensive measurement system with the help of a diamond counter-anvil high-pressure device. . They found that under the effect of pressure, the thermoelectric figure of merit first increased like a hill climb, reaching a maximum value of 1.7 near 30,000 atmospheres, and then slowly decreased as the pressure further increased.
By comparing the experimental and theoretical results, the researchers found that at the place where the thermoelectric figure of merit is best, the material undergoes a topological phase change from the original ribbon insulator to a topological crystal insulator. The latter, as a new type of quantum phenomenon, has been a focus of material science and condensed matter physics in recent years. This study correlated the thermoelectric effect with topological insulators, and at the same time discovered a new way to achieve topologically insulated states, that is, a clean and effective method of compressing the lattice. (Reporter Yan Jie)
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