Transcript Thermoelectric Materials

Utilizing Waste Heat for Electricity Generation by
‡
Thermoelectrics
Jibran Khaliq1, Qinghui Jiang1, Haixue Yan1,2 Kevin Simpson3, and Michael J. Reece1,2
1School of Engineering and Material Science, Queen Mary University of London, London, E1 4NS, UK
2Nanoforce Technology Limited, London, E1 4NS, UK
3European Thermodynamics Limited, Leicester LE8 0RX, UK
Email: [email protected], [email protected]
1. Motivation
More than 60% heat is wasted while burning fuel. This waste heat can be utilized as a
source of free energy. Thermoelectric materials can convert this waste heat from different
sources directly into electricity. Thermoelectric materials are environmentally friendly, have
no moving parts and are light weight, which make them excellent energy harvesting
materials. Their efficiency is represented by dimensionless figure of merit zT which depends
on high electrical conductivity and seebeck coefficient and low values of thermal
conductivity.
2. Applications
Mars Curiosity Rover: Powering itself
through thermoelectric generator (Photo
Cell phone charger: Uses heat from the feet
Credit: NASA/JPL-Caltech)
3. Objective
The objective of our research is to
optimize thermoelectric properties of
CoSb3 by using Phonon Glass Electron
Crystal concept i.e. to reduce thermal
conductivity without affecting electrical
conductivity and seebeck coefficient.
Thermoelectric generator in car: Uses
heat from engine
Thermoelectric Cooler
5. Results and Discussions
Co
Sb
Yb
4. Materials and Methods
Single
phase
powders
of
CoSb3,
CoSb2.85Te0.15 and Yb0.075CoSb2.85Te0.15
were obtained by mechanical alloying.
Ceramic disk of 20 millimetre diameter
were fabricated (relative density >97%) by
Spark Plasma Sintering.
Sb was substituted for Te in CoSb3
(CoSb2.85Te0.15) to enhance electrical
conductivity and seebeck coefficient.
Two naturally formed cage in the crystal
structure of CoSb3 was filled by Yb
which ‘‘rattle’’ inside the cage to reduce
thermal conductivity only.
Schematic of Spark Plasma Sintering (SPS) furnace
Electrical Conductivity and seebeck
coefficient were measured using Namicro
thermoelectric measurement equipment,
under vacuum and thermal conductivity
were measured using LFA 457, DSC and
density measurement by Archimedes'
Principle.
Acknowledgement
Decrease in thermal conductivity
with Yb addition in CoSb2.85Te0.15. No
effect on electrical conductivity and
seebeck
coefficient.
zT
value
increased to ~ 0.7.
6. Conclusion
A very low thermal conductivity of 2.19 W/m.K was observed in
Yb0.075CoSb2.85Te0.15 without affecting electrical conductivity and
seebeck coefficient of CoSb2.85Te0.15. A high zT value of ~0.7 is
reported for Yb doped and Te substituted CoSb3.
‡
Work Submitted to Scripta Materialia
School of Engineering and Materials Science