Scientists develop lead-free materials to transform waste warmth to electrical energy

Vijay Mohan

Today News Online Service

Chandigarh, February 23

Indian scientists have found a new lead-free material which can efficiently convert waste heat to power small home appliances and automobiles.

So far, most of the efficient thermoelectric materials developed by scientists use lead as a major constituent element, thereby restricting their use for mass-market applications.

Scientists from Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru, have identified a lead-free material called ‘Cadmium doped Silver Antimony Telluride’ which can efficiently allow recovery of electricity from ‘waste heat’, marking a paradigm shift in the thermoelectric puzzle, the Ministry of Science and Technology announced on Tuesday.

Thermoelectric energy conversion allows generation of electrical voltage when one end of a material is heated while keeping the other side cold. Finding an efficient material to realise this scientific principle has been a daunting task for scientists. It entails fitting in three seemingly different properties — high electrical conductivity of metals, high thermoelectric sensitivity of semiconductors and low thermal conductivity of glasses — into a single material.

The team, led by Prof Kanishka Biswas, doped (meaning internally introduced) Silver Antimony Telluride with Cadmium and used an advanced electron microscopy technique to visualise the resultant ordering of atoms in nanometre scale. The nanometre-scale atomic ordering scatters phonons that carries heat in a solid material and enhances electrical transport by delocalizing the electronic state in the material.

Previously reported state-of-the-art material is exhibiting thermoelectric figure of merit in the range 1.5-2 at the mid-temperature range of 400-700 degree Kelvin. The Indian team has reported a record increase in thermoelectric figure of merit of 2.6 at 573 degree Kelvin. This can provide heat for electrical energy conversion with an efficiency of 14 per cent.

The findings have been published in international peer-reviewed journal “Science”. Efforts are on to commercialise the high-performance thermoelectric materials and devices; in collaboration with the industry where lots of waste heat is generated.

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