Thermoelectric new material prevents heat waste

Fossil fuels have created a modern society by generating heat, but most of the heat in this process has been wasted. Researchers have tried to recover some of the heat using semiconductor devices called "thermoelectrics," but most of them are still very inefficient and expensive.

Now, scientists in Illinois, USA, report that they have used the cheap common materials to create the most efficient thermoelectric recovery so far. The researchers said that in the process, they gained valuable experience and could eventually make the material's efficiency meet the needs of a wide range of applications. If it can achieve a wide range of applications, thermoelectricity can provide power for automobiles in the future, and clean up the energy released from boilers and power plants.

Thermoelectric devices are semiconductor slabs that have strange but useful characteristics: heating on one side can generate voltage for driving current and power equipment. In order to obtain the voltage, the thermoelectric must be a good electrical conductor and a poor thermal conductor. Unfortunately, the conductivity and thermal conductivity of materials tend to go hand in hand, so materials with high thermoelectric efficiency are difficult to obtain. Scientists usually use the ZT value to mark the characteristics of high thermoelectricity efficiency, and the maximum application of thermoelectric ZT should be at least 3.

A few years ago, the team led by Northwestern University chemist Mercouri Kanatzidis discovered that the ZT value of lead telluride (PbTe) could reach 2.2. Kanatzidis and his colleagues were encouraged and began testing PbTe's chemical closest relatives. One of them is tin selenide (SnSe). Researchers synthesize samples of tin selenide using different methods. The results showed that the b-axis sample had better electrical conductivity and lower thermal conductivity, with a ZT value of 2.6. Kanatzidis said that the key to ultra-low thermal conductivity seems to be the arrangement of the tin and selenium atoms. This pattern seems to help the atoms flex when they are subjected to thermal vibrations, thereby reducing the thermal conductivity of SnSe. The results of the study were published in the recent issue of Nature.

"I was surprised," said Joseph Heremans, a physicist at the Ohio State University. "This is a wonderful result for this field." Heremans believes that in addition to marking a big step toward thermoelectricity with a ZT value of 3. In addition, the new materials also provide experience for future research methods. Researchers will attempt to increase the conductivity of semiconductors by enhancing trace amounts of “doped” atoms while also retaining the critical pleated atomic arrangement. If someone can successfully produce high ZT materials, new, cheaper hybrid car engines will be produced. In a hybrid car engine, the internal combustion engine does not provide power to the car, but instead generates heat that is then converted by the thermoelectric to an electric drive motor.

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