November 14, 2012

Michigan State University is home to one of the most advanced thermoelectric power generation research groups in the world. And now, a new thermoelectric material is on the horizon.

Professor Don Morelli (right) and MSU graduate student Xu Lu discuss the structure of the mineral tetrahedrite.

Researchers in MSU's Center for Revolutionary Materials for Solid State Energy Conversion—an Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy—are developing a thermoelectric material based on natural mineral tetrahedrites. Their work was recently published in the online journal Advanced Energy Materials.

Thermoelectric materials can be used to convert waste heat into electricity and have the potential to improve energy efficiency in industry, transportation, and everyday life.

Scientists have been working to develop new thermoelectric materials over the past 15 years, but they are faced with challenges. While several new, more efficient materials have been discovered, many of these are not suitable for large-scale applications because they are derived from rare or toxic elements, or the synthesis procedures are complex and costly.

The EFRC researchers set out to discover new thermoelectric materials that are inexpensive, environment-friendly, easy to synthesize, and composed of earth-abundant elements.

"What we've managed to do is synthesize some compounds that have the same composition as natural minerals. The mineral family that they mimic is one of the most abundant minerals of this type on earth—tetrahedrites," said Donald Morelli, EFRC director and professor in MSU's Department of Chemical Engineering and Materials Science.

"We used the mineral as a source of thermoelectric material. By modifying its composition in a very small way, we were able to produce highly efficient thermoelectric materials. We synthesized in the laboratory the same compositions that occur in nature.

"Our research also shows that the natural mineral itself can be mined and used directly, with very little additional processing."

Morelli said that this work creates a new paradigm for thermoelectric materials. "Typically, you'd mine minerals out of the earth, purify them into their individual elements, and then recombine those elements into new compounds that you anticipate will have good thermoelectric properties. But that process costs a lot of money and it takes a lot of time," he said. "Our method bypasses much of that. It saves tremendously in terms of processing costs."

The researchers expect that this discovery could pave the way to many new, low-cost thermoelectric generation opportunities, with applications that include waste heat recovery from industrial power plants, conversion of vehicle exhaust gas heat into electricity, and generation of electricity in home heating furnaces.

This work was supported by the U.S. Department of Energy/Office of Science—at MSU and UCLA through the Center for Revolutionary Materials for Solid State Energy Conversion, and at the University of Michigan through their EFRC, the Center for Solar and Thermal Energy Conversion.

In August 2009, the Office of Basic Energy Sciences in the U.S. Department of Energy's Office of Science established 46 Energy Frontier Research Centers (EFRCs), including the one at MSU. These centers involve universities, national laboratories, nonprofit organizations, and for-profit firms, and were selected by scientific peer review and funded at $2-5 million per year for a five-year initial award period. The centers conduct fundamental research focusing on one or more of several "grand challenges." The EFRCs harness the most basic and advanced discovery research in a concerted effort to establish the scientific foundation for a fundamentally new U.S. energy economy. The outcome will decisively enhance U.S. energy security and protect the global environment in the century ahead.

Other MSU researchers working with Morelli in the EFRC are Eldon Case, professor, and Jeff Sakamoto, assistant professor, Department of Chemical Engineering and Materials Science; Tim Hogan, professor, Department of Electrical and Computer Engineering; Harold Schock, professor, Department of Mechanical Engineering; and Subhendra (Bhanu) Mahanti, professor, Department of Physics and Astronomy.

In addition to U of M and UCLA, other institutions involved with the MSU-based EFRC are Northwestern University, the Ohio State University, Wayne State University, and Oak Ridge National Laboratory.

In addition to Morelli, authors of the paper titled "High Performance Thermoelectricity in Earth-Abundant Compounds Based on Natural Mineral Tetrahedrites" include: Xu Lu, MSU PhD student; Yi Xia, PhD student, UCLA; Fei Zhou, postdoctoral scholar, UCLA; Vidvuds Ozolins, professor, UCLA; Hang Chi, PhD student, U of M; Xiaoyuan Zhou, postdoctoral scholar, U of M; and Ctirad Uher, professor, U of M.