Materials for Converting Waste Heat to Electricity Pass Critical Milestone
The new thermoelectric material consists primarily of lead and tellurium; past studies found that lead telluride was the best thermoelectric system at the kind of high temperatures one might find in engines and other hot spots. The researchers adopted three different techniques for soaking up energy from phonons. Within the material, grains of semiconducting lead telluride that are hundreds to thousands of nanometers wide absorb phonons of longer wavelengths. Also, precipitates of strontium telluride 2 to 10 nanometers wide target shorter wavelengths. Finally, trace amounts of sodium injected within the material’s crystalline structure go after the shortest wavelengths. As a result, the material achieves a world-record ZT of 2.2. “That’s conservatively between 15 and 30% more efficient than the previous record-holder,” researcher Kanatzidis says.