Sol-gel preparation of doped-metal oxide nanostructures for the thermoelectric conversion of energy

SSCI-VIDE+CDFA+SMR:AVC:SDAInternational audienceHigh-efficiency thermoelectric (TE) materials are important for power-generation devices designed to convert waste heat into electrical energy or to use in solid-state refrigeration. These applications require innovative materials which not only possess high conversion efficiency but should also be non-toxic and have high chemical stability in air over a wide range of temperature. The TE efficiency is related to high dimensionless number called figure of merit ZT, which is a combination of three material properties: Seebeck coefficient, electrical conductivity and thermal conductivity. The advent of nanotechnology has led to a dramatic effect on the development of TE materials and has resulted in the synthesis of nanostructured materials with better thermoelectric properties (as compared to conventional materials) mainly because of the reduction of the lattice thermal conductivity.As part of our ongoing project ‘Othello’ to develop metal oxide-based thermoelectric materials, we are currently studying TiO2-based materials, which are cheap, chemically stable and non- toxic in nature, although the poor electronical conduction of TiO2 remains a technological limitation to meet the requirements for thermoelectric applications. This talk will present sol-gel synthesis of Nb5+-doped TiO2 and TiO2-SnO2 nanoparticles, their conversion to dense ceramic pellets using spark plasma sintering (SPS) technique and their thermoelectric properties. Impact of the temperature of SPS process on the densification, nanostructuration and the dopant distribution will be discussed

Sol-gel preparation of doped-metal oxide nanostructures for the thermoelectric conversion of energy

SSCI-VIDE+CDFA+SMR:AVC:SDAInternational audienceHigh-efficiency thermoelectric (TE) materials are important for power-generation devices designed to convert waste heat into electrical energy or to use in solid-state refrigeration. These applications require innovative materials which not only possess high conversion efficiency but should also be non-toxic and have high chemical stability in air over a wide range of temperature. The TE efficiency is related to high dimensionless number called figure of merit ZT, which is a combination of three material properties: Seebeck coefficient, electrical conductivity and thermal conductivity. The advent of nanotechnology has led to a dramatic effect on the development of TE materials and has resulted in the synthesis of nanostructured materials with better thermoelectric properties (as compared to conventional materials) mainly because of the reduction of the lattice thermal conductivity.As part of our ongoing project ‘Othello’ to develop metal oxide-based thermoelectric materials, we are currently studying TiO2-based materials, which are cheap, chemically stable and non- toxic in nature, although the poor electronical conduction of TiO2 remains a technological limitation to meet the requirements for thermoelectric applications. This talk will present sol-gel synthesis of Nb5+-doped TiO2 and TiO2-SnO2 nanoparticles, their conversion to dense ceramic pellets using spark plasma sintering (SPS) technique and their thermoelectric properties. Impact of the temperature of SPS process on the densification, nanostructuration and the dopant distribution will be discussed

In situ X-ray diffraction study of a TiO2 nanopowder Spark Plasma Sintering under very high pressure

International audienceWe investigated the effect of very high pressure on the sintering temperature, phase transition and the grain growth during Spark Plasma Sintering (SPS) of a 15 nm TiO2 nanopowder. Using in situ synchrotron X-ray diffraction during sintering at 1.5 and 3.5 GPa, we followed the evolution of the crystalline phases and the crystallite size as a function of temperature. In comparison, in the laboratory, SPS experiments were performed on two original facilities: A Paris-Edinburgh press and a high-pressure module adapted to standard SPS equipment. We studied the effect of the pressure on the sintering in the range 76 MPa to 3.5 GPa. We have shown that highly dense nanostructured ceramics can be prepared under very high pressure at low sintering temperatures. At 1 GPa, we limited the grain growth to an average size of 233 nm by heating at only 560 °C, and achieved a relative density of 98 %