Ultra-high temperature synthesis of high-performance Zintl thermoelectrics

Lead Research Organisation: Heriot-Watt University
Department Name: Sch of Engineering and Physical Science


Technologies that enable the efficient use of energy could have an enormous impact on the most pressing issues of today: global warming and the reliance on ever-dwindling supplies of fossil fuels.

The proposed research addresses this topical challenge through the investigation of the next generation of thermoelectric materials that harvest waste heat and transform it into useful electricity. In particular, the research is focused on thermoelectric materials that can operate at high temperatures, which is essential as the Carnot efficiency (the thermodynamic maximum) increases with temperature difference.

The scientific challenge is to optimise three competing material parameters; the Seebeck voltage; the electrical and thermal conductivity, and to do this in a material with good temperature stability.

The novelty of the proposed research derives from the use of ultra-high temperature synthesis to achieve temperature stability, and the synergistic exploitation of Zintl chemistry and interfaces in nanocomposites to obtain large thermoelectric figures of merit.

Zintl phases are key high-performance thermoelectric materials because the simultaneous presence of ionic and covalent regions enables a more independent optimisation of the thermoelectric parameters compared to electronically homogeneous materials. Two classes of promising Zintl-type phases have been identified, and the performance of outstanding bulk materials will be further enhanced through the use of interfaces in nanocomposites.

This ambitious and transformative research programme will contribute towards the development of high-performance thermoelectric materials operating at temperatures most suitable to power generation, enabling 20-30% energy conversion efficiencies. The research will also lead to an increased understanding of the relation between composition, structure and thermoelectric properties.

Planned Impact

The large scale implementation of power generation from waste heat depends primarily on the discovery of thermally stable high-performance thermoelectric materials, which the proposed research intends to address. The most promising application areas are in energy recovery from hot exhaust gases in automobiles, and exploitation of solar infrared radiation not collected using photovoltaic cells.

About 60% of the energy stored in petrol is lost as heat in combustion engines. Most large car manufacturers, including general motors and BMW, are looking to integrate thermoelectric devices into the exhaust system (temperatures of the order of 600 degrees Celsius) and use the electricity to power the on-board electronics and air-conditioning. This makes the alternator redundant, which reduces roll friction, and results in substantial reductions in fossil fuel consumption.

About 40% of the solar spectrum is in the infrared domain and is not used by conventional solar cells. The goal is to use photovoltaic and thermoelectric cells in tandem to utilize the whole solar spectrum. In this scenario the solar light would be concentrated using optical lenses to temperatures above 500 degrees Celsius to achieve sufficiently large temperature gradients.

Achieving maximum impact relies on effective communication of the proposed research to both society and potential industrial partners.

A sustainable world energy supply is of great importance for the United Kingdom. The contribution this research makes will be communicated through a number of public engagement activities, including writing a general interest article and presentations aimed at the tax-paying public.

The research has a clear potential economic impact if it results in the discovery of high-performance materials. UK industry could play a role in the bulk manufacture of these materials, in fabrication of the devices, or in the design and implementation of bespoke thermoelectric modules using high-efficiency materials. A strong effort will be made to engage with possible industrial partners. This will not just focus on chemical companies that manufacture materials but also on engineering companies that may wish to exploit thermoelectric modules in their products. The initial contact will be aimed at gauging interest and exploring possible collaborations. In case of the discovery of commercially interesting materials the intellectual property will be protected through Heriot-Watt University. The established contacts will then be used to explore possible scale-up and fabrication of devices, which requires a significant amount of engineering expertise.


10 25 50
Description Thermoelectric devices use semiconductors to harvest waste heat and convert this into electricity. Over the course of the grant we have demonstrated that nanostructured half-Heusler composite materials have promising energy conversion efficiencies. Considerable time and effort has been spent in carefully preparing new compositions and characterising their structures and thermoelectric performance. We found that off-stoichiometric compositions such as TiNi1+ySn can sustain improved performance, and that sample processing is vital in obtaining high-performance materials. This work has been taken forward in EPSRC grant EP/N01717X/1 "Nanostructured half-Heuslers for thermoelectric waste heat recovery".
Exploitation Route Improved thermoelectric materials based on abundant elements could lead to widespread application of this technology. Findings could be used by researchers interested in up-scaling and device fabrication.
Sectors Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology,Other

Description This EPSRC First Grant has enabled the PI to start new research into Zintl-type thermoelectric materials. The main outputs are journal publications but contacts have been made with possible industrial partners, including European Thermodynamics Ltd, an UK SME specialising in bespoke thermoelectric heat management solutions and Johnson Matthey who might be interested in upscaling thermoelectric materials.
Sector Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

Description INSPIRE Physical Sciences: A synergy for next generation materials science
Amount £50,457 (GBP)
Funding ID EP/K036408/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 04/2013 
End 09/2014
Description Nanostructured half-Heuslers for thermoelectric waste heat recovery
Amount £365,000 (GBP)
Funding ID EP/N01717X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2016 
End 01/2019
Description Reduced titanium and niobium oxide thermoelectrics
Amount £146,000 (GBP)
Funding ID RPG-2012-576 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 02/2013 
End 02/2016
Description General interest article on Thermoelectric Materials in Education in Chemistry 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact This is a focus article published in the March 2012 issue of Education in Chemistry, a Royal Society of Chemistry magazine that is distributed among all secondary schools in the UK.

Creating wider appreciation of thermoelectric materials, and thermoelectric waste heat recovery among secondary school pupils.
Year(s) Of Engagement Activity 2012
URL http://www.rsc.org/Education/EiC/issues/2012March/thermoelectric-materials-nanoparticles.asp