The Purdue researchers have used the ZT number to calculate the maximum efficiency that is theoretically possible with a material.
"We analyze the material abundance, the cost, toxicity and performance, and we established a single parameter called the efficiency ratio," Wu said.
Although high-performance thermoelectric materials have been developed, the materials are not practical for widespread industrial applications.
"Today's higher performance ones have a complicated composition, making them expensive and hard to manufacture," Wu said. "Also, they contain toxic materials, like antimony, which restricts thermoelectric research."
The nanocrystals are a critical ingredient, in part because the interfaces between the tiny crystals serve to suppress the vibration of the crystal lattice structure, reducing thermal conductivity. The materials could be exhibiting "quantum confinement," in which the structures are so tiny they behave nearly like individual atoms.
"This means that, as electrons carry heat through the structures, the average voltage of those heat-carrying electrons is higher than it would be in larger structures," Finefrock said. "Since you have higher-voltage electrons, you can generate more power."
This confinement can raise the ZT number.
A U.S. patent application has been filed for the fiber-coating concept.
Future work could focus on higher temperature annealing to improve efficiency, and the researchers also are exploring a different method to eliminate annealing altogether, which might make it possible to coat polymer fibers instead of glass.
"Polymers could be weaved into a wearable device that could be a cooling garment," Wu said.
The researchers also may work toward coating the glass
|Contact: Emil Venere|