Indian scientists develop efficient thermoelectric material that can convert waste heat into electricity for cars

Thermoelectric energy conversion generates voltage when one end of a material is heated and the other end is kept cool. Finding an efficient material to realize this scientific principle has always been a difficult task for scientists, requiring the material to have three seemingly different properties, namely the high electrical conductivity of metals, the high thermoelectric sensitivity of semiconductors, and the low thermal conductivity of glass. So far, most of the efficient thermoelectric materials developed by scientists use lead (Pb) as the main component, which also limits its application in the mass market.

Thermoelectric material performance index (Image source: Jawaharlal Nehru Center for Advanced Scientific Research)

According to foreign media reports, scientists at the Jawaharlal Nehru Center for Advanced Scientific Research (JNCASR) in Bangalore, India, have discovered a lead-free material called cadmium (Cd)-doped silver antimony telluride (AgSbTe2) that can efficiently recover electricity from "waste heat", which also marks a major change in the field of thermoelectricity. The JNCASR is an independent research institute of the Department of Science and Technology (DST) of the Indian government, led by Professor Kanishka Biswas.

Professor Kanishka Biswas and his team doped silver antimony telluride with cadmium and used an advanced electron microscopy technique to visualize the resulting atomic ordering of the material at the nanoscale. This nanoscale atomic ordering scatters phonons, which carry heat in solids, and enhances electrical transport by delocalizing electronic states in the material.

The most advanced materials previously studied by scientists have a thermoelectric quality factor (ZT) of 1.5 to 2 at a temperature range of 400-700 K. The Indian team broke the record, with a thermoelectric quality factor of 2.6 at a temperature of 573 K and a waste heat to electricity conversion rate of 14%. Currently, Professor Biswas is trying to commercialize the high-performance thermoelectric material and equipment, and is working with Tata Steel because steel power plants generate a lot of waste heat.