Manufacturing and Characterisation of a Thermoelectric Materials based on Boron Doped Nanocrystalline Diamond Foils

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Thermoelectric generators (TEG) based on the Seebeck Effect can directly produce electrical current from the waste heat generated by cars or power plants for instance. The established TEG materials currently enable no economical use due to its toxicity, its rare availability (Bismuth- and Lead Tellurides) or its low efficiency (Silicon Germanium).Single crystalline and microcrystalline diamond have a very high thermal conductivity (ca. 2000W/mK) and a very low electrical conductivity, therefore diamond seems to be unsuitable as thermoelectric material. Nanocrystalline diamond foils can be produced by chemical vapour deposition of boron doped diamond on temperature stable templates. After deposition a controlled delamination of the complete nanodiamond layer as nanodiamond foil is possible. It is a promising thermoelectric material, due to its good electrical conductivity and low thermal conductivity (ca. 2 W/mK). Nano diamond is very stable at elevated temperatures (ca. 600°C in air, ca. 1100°C without oxygen). These properties should enable high thermoelectric efficiencies (ZT- value > 2-3). In this project we want to produce boron-dope Nanocrystalline diamond foils with by variation of the HF-CVD process parameters (pressure, methane content, boron content, coating temperature). The thermoelectric properties (Seebeck coefficient, thermal and electrical conductivity) will be measured. Furthermore a thermoelectric generator should be built and characterized by using the new boron-doped foils (p-conductivity) and "poor" (low effiency) N-doped carbon foils (n-conductivity).