A team of researchers from the Clemson Department of Physics and Astronomy and the Clemson Nanomaterials Institute (CNI), in collaboration with a renowned expert in thermoelectric materials, has created a foolproof method for assessing the quality of thermoelectric materials.
A research team including Assistant Professor Sriparna Bhattacharya, Engineer Herbert Behlow, and CNI Founding Director Apparao Rao from the Department of Physics and Astronomy and working with renowned researcher H. J. Goldsmid, professor emeritus at the University of New South Wales (UNSW) in Sydney, Australia, developed a comprehensive approach for determining the effectiveness of thermoelectric materials.
H.J. Goldsmid is widely recognized as the "father of thermoelectrics" for his pioneering research in thermoelectric materials. Professor Bhattacharya, a Research Assistant Professor, initially reached out to Goldsmid on LinkedIn, where she informed him that she had validated one of his theoretical predictions during her graduate studies at Clemson University.
Materials Generating Electricity
After some time, Bhattacharya shared a paper co-authored by her and Rao with Goldsmid after she joined the research group of Rao. Goldsmid told her he had a new method for studying thermoelectrics and shared his one-page theory with her. Despite being 89 years old, Goldsmid was enthusiastic about collaborating with the CNI researchers, seeing Bhattacharya as a member of his own research "family."
Thermoelectric materials generate electricity using a temperature difference (DT). These materials can convert heat into electricity (Seebeck method) or electricity into cooling (Peltier method) and are therefore used for power generation and refrigeration. They are used in various applications such as NASA space missions, seat warmers and coolers in vehicles, and many others, as stated by Phys.
A figure-of-merit measures the effectiveness of thermoelectric materials referred to as "zT," which considers the material's temperature, electrical conductivity, and thermal conductivity. The conventional method of determining zT calls for two measurements utilizing distinct equipment sets, sometimes leading to inaccurate research results. This is because sometimes researchers mistakenly measure electrical conductivity (charge flow) and thermal conductivity (heat flow) along different directions in their sample when switching between different instruments.
ALSO READ : Nanotechnology Against Obesity: New Cationic Nanomaterials Target and Remodel Enlarged Fat Cells
Combining Conductor and Semis
The Peltier cooling method had not been used earlier for evaluating zT due to a high DT or the maximum achievable difference in temperature between the cold junction and the ambient. The scientists have employed thermocouples containing a metal and a semiconductor junction to decrease the DT to a much narrower range, enabling a higher resolution determination of temperature-dependent zT, as Behlow mentioned. He also emphasized the concept of using a combination of metal and a semiconductor to lower DT right there in front of us, but it was Professor Goldsmid who recognized it and proposed this new method for measuring zT.
The experimental setup that we developed at CNI (with the help of the Department of Physics and Astronomy Instrument Shop) to test Professor Goldsmid's theory guarantees that the charge flow and the heat flow are measured in the same direction within the sample, said Rao. The researcher added that their method is designed to provide accurate zT measurements. Isabel Rancu, a high school student from the South Carolina Governor's School for Science and Mathematics, also contributed to this research. Rancu, who participated in the research through Clemson's Summer Program for Research Interns independently confirmed the model calculations reported by Behlow.
During her doctoral research, senior Lecturer Pooja Puneet synthesized the bismuth telluride sample used in the study from the Department of Physics and Astronomy.
The study, titled "Thermoelectric figure-of-merit from Peltier cooling," was published in November in the Journal of Applied Physics. It was selected as an "editor's pick," which the team sees as a tribute to Goldsmid and his contributions to the field.
Check out more news and information on Nanotechnology in Science Times.
