High Performance Thermoelectric modules based on bulk materials

After defining the targeted microstructure to get high ZT nanostructured Bi2Te3 during the first year [1], CEA-LITEN team performed thermoelectric system simulations and optimizations to define the specific designs for thermoelectric coolers which will be integrated in the avionic and automotive demonstrators. Following those simulations, specific TEC were fabricated and experienced by CEA, SHT, Thales Avionic and CRF. From the first tests under operational conditions, new designs are under study to enable higher cycling reliability while keeping the same thermoelectric performances.

 

 

 

Automotive demonstrator TEC optimization to maximize COP and minimize electrical consumption (top left), and AC automotive optimization regarding power consumption and air flow (top right) and respective manufactured TEC (bottom left) and (bottom right)

 

-[1] G. Bernard-Granger et al, Influence of nanosized inclusions on the room temperature thermoelectrical properties of a p-type bismuth–tellurium–antimony alloy, Acta Materialia 60 4523–4530, 2012

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2 Lasers Raman Thermometry

The Catalan Institute of nanotechnology (ICN) developed a novel high resolution contactless technique for thermal conductivity determination and thermal fields mapping suitable to study bulk samples, thin films, and nanowires. The setup relies on creating a thermal distribution using a heating laser, while a second laser probes the local temperature through the spectral position of a Raman active mode. The spatial resolution of this technique can be as small as 500 nm, whereas its temperature accuracy is ±2 K.

ICN validated this technique investigating the thermal properties of free-standing single crystalline Si membranes with a thickness of 250 nm. In order to apply this technique, the material under investigation ought to meet the following requirements:

  • Temperature Sensor:. a Raman active mode must be detectable in order to probe the local temperature. This mode will ideally exhibit a strong temperature dependence (∂ω/∂T) to be a good temperature sensor. A calibration of the Raman shift versus temperature must be known in advance.
  • Excitation Source: the sample should have a reasonable absorbance in the spectral region of the heating laser to set up the temperature distribution. The absorbed power needs to be determined for each experimental conditions.
  • Dimensionality: the sample must be of 1- or 2-dimensions with lateral size larger than the optical resolution (≈ 300 nm). It is also possible to study 3-dimensional structures provided that the heat distribution has a spherical symmetry with respect to the heating laser spot.

 

-(a) Schematics of the 2-Laser Raman Thermometry experimental setup. To lower laser is used as heating source, whereas the upper laser probes the local temperature through the spectral shift of the longitudinal optical Raman mode of Si. (b) 2-dimensional thermal map of a 250 nm thick free-standing Si membrane. A projection of the thermal field is also shown in a lower plane.

 

Further details: http://arxiv.org/abs/1312.7705

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New Thermal Interface Material

A new type of nano composite polymer matrix solder with low thermal resistance joints and high reliability has been developed with collaboration of researchers from SHT and Chalmers University of Technology. The related paper ' A new solder matrix nano polymer composite for thermal managment application' was recently pubulished in Composites Science and Technology, 94 (2014) 54-61. The composite shows high heat transfer capability and lower elastic modulus compared to pure solder alloy, and reliable thermomechanical performance.

-[2] Carl Zandéna, Xin Luoa, Lilei Yec and Johan Liu, A new solder matrix nano polymer composite for thermal management applications, Composites Science and Technology, 94 (2014) 54-61