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Thermoelectric measurements

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The development of thermoelectric materials at DLR focuses on the high temperature range (currently up to 900 °C, in future beyond 1000 °C). An extensive spectrum of measuring techniques (temperature dependence of the Seebeck coefficient, thermal and electrical conductivity, Hall coefficient and thermoelectric figure of merit) is required for comprehensive functional characterisation of high temperature thermoelectrics, which involves a wide temperature range spanning from ambient up to highest relevant temperatures.
One focus of current developments in laboratory apparatuses for those high temperature measurements is the implementation of long-term stable contact thermocouples operated in contact to silicide and oxide sample materials.
Rarely available characterisation methods [http://www.dlr.de/wf/institut/anlagen/cvfm] as well as unique systems development are operated at DLR, among them

• Laser flash apparatus for determination of thermal diffusivity 
• Thermogenerator test facility for efficiency determination of thermoelectric energy converters
• Temperature dependent measurement of Seebeck coefficient and electrical conductivity from room temperature up to 700 °C 
• Hall facility for the examination of electric transport properties 
• CTEM – combined thermoelectric measurement (simultaneous measurement of the Seebeck coefficient, electrical and thermal conductivity, as well as the thermoelectric figure of merit) 
• Seebeck micro-thermoprobe for spatially resolving determination of thermoelectric properties at surfaces of electrically conducting materials.

The institute offers characterisation services of thermal and electric functional properties for co-operation partners as well as for external customers (on order).
Standardisation of thermoelectric measurements is operated in European cooperation with the NEDO Laboratory for Thermoelectric Engineering, Cardiff, UK and the University of Aarhus, DK and is to be extended to a Europe-wide network.
Accompanying the increasing transfer of thermoelectric technologies to an industrial level, the field of experience on automated thermoelectric measurement and data acquisition at DLR is to be potentially expanded to include design and development of complete and customised measuring systems for commercial manufacturing.