NANOSICON

High-temperature stable nano-structured silicides for highly efficient thermogenerators and their contacting technology

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 Obiettivo del progetto (Objective)

'Deficiency of natural energy resources on Earth makes advanced energy management a challenge. Efforts are taken to harness cheap, inexhaustible, eco-friendly renewable sources of energy. Among these, thermoelectric (TE) conversion is a promising principle. Best materials for TE application are non-conventional heavily doped semiconductors. In particular, high temperature stable silicides (higher manganese silicides = HMS, CrSi2 and others) represent suitable candidates for demanded TE applications operable at high temperature. A main aim of TE materials development is to improve the figure of merit ZT, which essentially depends on the energy band structure and scattering of carriers and phonons in the material. It is planned to investigate qualitatively the transport behaviour of HMS compacted from nano-sized powders, to optimize its properties by chemical synthesis, and to reach a reduction of the thermal conductivity in nano-crystalline material. Starting from the synthesis of nano-powders by melting and ball milling, forming of a nano-structure with suitable scaling will be optimized by a rapid hot pressing technology. CrSi2 and other high temperature silicides will be optimized in a similar way for high electrical and thermal conductivity. They shall be applied as contacting materials and interlayers, ending up to advanced materials and technology procedures for high temperature thermogenerators. Materials will be characterized by XRD, SEAD (structure), TEM, SEM (morphology), EDAX (analysis). Having achieved the targeted nano-structure, the TE properties will be measured in dependence on temperature for optimising the application-relevant material parameters. The performance of thermogenerator devices based on the new solutions will be tested by unique measuring techniques of the host. The fellow will deepen his knowledge and experience on TE materials and thermogenerator technology for high temperature and is expected to develop superior contacting methods.'

Introduzione (Teaser)

New thermoelectric materials have been developed with improved performance in making electricity from heat. The technology has stimulated worldwide interest in many fields, including waste-heat recovery in cars.

Descrizione progetto (Article)

Thermoelectric (TE) devices are solid-state devices in which electricity flows through a solid semiconductor. They convert temperature differences directly into electricity and vice versa. The potential applications are numerous, especially for cooling and electric power generation. TE devices have no moving mechanical parts and so are very reliable and quiet in operation. They are also very small and environmentally friendly.

Promising materials for TE generators are silicides. These are binary compounds of silicon, such as magnesium silicide, or their solid solutions, which are mixtures of two crystalline solids that co-exist as a new crystalline solid.

The main disadvantage of TE materials relates to their efficiency of energy conversion which is still low and limits their widespread development and use. The objective EU-funded 'High-temperature stable nano-structured silicides for highly efficient thermogenerators and their contacting technology' (Nanosicon) project set out to increase their efficiency.

Project partners studied the high temperature TE properties of magnesium silicide and its solid solutions and examined the influence of doping. The latter involves the addition of certain impurities to reduce the semiconductor's electrical resistance. They then characterised the resulting materials according to their electronic and thermal transport properties.

Project efforts achieved remarkable improvements in the potential performance of these semiconductors in TE applications. This makes these materials excellent candidates for thermogenerator applications. One area of relevance is for automobiles where waste heat from a car's exhaust can be converted into electricity.