Lead free material identified to convert waste heat to electricity

New Delhi, Feb 23 (KNN) Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru has identified a lead-free material called Cadmium (Cd) doped Silver Antimony Telluride (AgSbTe2) which can efficiently allow recovery of electricity fr0m waste heat marking a paradigm shift in the thermoelectric puzzle. It can convert waste heat to power our small home equipment and automobiles.

Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru is an autonomous institution of the Department of Science & Technology (DST).

Thermoelectric energy conversion allows the generation of electrical voltage when one end of the material is heated while keeping the other side cold. Finding an efficient material to realize this scientific principle has been a daunting task for scientists.

It entails fitting in three seemingly different properties into a single material-- high electrical conductivity of metals, high thermoelectric sensitivity of semiconductors, and low thermal conductivity of glasses.

Most efficient thermoelectric materials developed by scientists so far use Lead (Pb) as a major constituent element, restricting their use for mass-market applications.

Prof. Kanishka Biswas and his group doped (internally introduced) Silver Antimony Telluride with Cadmium (Cd) and used an advanced electron microscopy technique to visualize the resultant ordering of atoms in nanometer scale. The nanometer-scale atomic ordering scatters phonons that carry heat in a solid and enhances electrical transport by delocalizing the electronic state in the material.

Previously reported state of the art material is exhibiting the thermoelectric figure of merit (ZT) in the range 1.5-2 in the mid-temperature range (400-700 K).   The team reported a record increase in thermoelectric figure of merit (ZT) to 2.6 at 573 K, which can provide the heat to electrical energy conversion efficiency to 14 %.

Prof. Biswas is now trying to commercialize the high-performance thermoelectric materials and devices; in collaboration with TATA steel where lots of waste heat is generated in steel power plant.

This work is supported by the Swarna-Jayanti fellowship and project fund fr0m Science and Engineering Research Board (SERB) and Department of Science & Technology (DST), India, along with support fr0m New Chemistry Unit (NCU) & International Centre for Materials Science (ICMS), JNCASR, Bangalore.