Plasma synthesis of nanostructures for improved thermoelectric properties

Petermann, Nils; Stein, Niklas; Schierning, Gabi; Theissmann, Ralf; Stoib, Benedikt; Brandt, Martin S.; Hecht, Christian; Schulz, Christof; Wiggers, Hartmut

doi:10.1088/0022-3727/44/17/174034

Cited by 107 publications

(84 citation statements)

References 67 publications

(62 reference statements)

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“…[ 100 ] This gasphase process can be easily upscaled for industrial processes with material output ranging from kg to tonnes per days and provides a highly reproducible synthesis of nm-sized nanoparticles. A sketch of the reactor concept for the nanoparticle synthesis from the gas phase is shown in Figure 12 a. Silane (SiH 4 ), germane (GeH 4 ), and the precursor materials for the intended doping (n-type doping: PH 3 , p-type doping: B 2 H 6 ) are homogeneously mixed in the gas phase and subsequently injected into a microwave induced plasma through a nozzle.…”

Section: Bulkmaterialsmentioning

confidence: 99%

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Nielsch

Bachmann

Kimling

et al. 2011

Advanced Energy Materials

221

138

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Thermoelectric materials could play an increasing role for the effi cient use of energy resources and waste heat recovery in the future. The thermoelectric effi ciency of materials is described by the fi gure of merit ZT = ( S 2 σ T )/ κ ( S Seebeck coeffi cient, σ electrical conductivity, κ thermal conductivity, and T absolute temperature). In recent years, several groups worldwide have been able to experimentally prove the enhancement of the thermoelectric effi ciency by reduction of the thermal conductivity due to phonon blocking at nanostructured interfaces. This review addresses recent developments from thermoelectric model systems, e.g. nanowires, nanoscale meshes, and thermionic superlattices, up to nanograined bulk-materials. In particular, the progress of nanostructured silicon and related alloys as an emerging material in thermoelectrics is emphasized. Scalable synthesis approaches of high-performance thermoelectrics for high-temperature applications is discussed at the end. 714 Physical FunctionalityThe direct conversion of heat to electricity in thermoelectric devices is based on the Seebeck effect (named for Thomas J. Seebeck, 1821). In thermoelectric cooling devices use is made of the Peltier effect (named for Jean C. A. Peltier, 1834). [3][4][5] The thermoelectric effects were initially examined in metals. These generate only small thermovoltages of a few tens of microvolts per Kelvin. The electrical potential difference generated per degree of temperature difference is called Seebeck coeffi cient, S , or thermopower.By using semiconductors, substantially higher thermovoltages of some hundreds of μ V/K can be achieved. For thermoelectric applications, low bandgap semiconductors, with typical charge carrier concentrations in the order of 10 19 /cm 3 , are considered most suitable. Apart from a large Seebeck coeffi cient, a good thermoelectric material additionally needs to exhibit a high electrical conductivity and a low thermal conductivity to obtain a large fi gure of merit, ZT , at a certain temperature. The interdependence of these quantities has limited the ZT to values around one for the best conventional thermoelectric materials. For semiconductors and thermoelectric materials, the heat conductivity depends on both free charge carriers (holes or electrons) and phonons: κ tot = κ El + κ Ph . The phonon-based thermal conductivity κ Ph is decoupled from the electric conductivity. Thus, numerous attempts for the optimization of the thermoelectric effi ciency ZT in nanostructures are based on a reduction of the heat transport by phonons.

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Section: Bulkmaterialsmentioning

confidence: 99%

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Nielsch

Bachmann

Kimling

et al. 2011

Advanced Energy Materials

221

138

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“…The images do not indicate the presence of an oxide shell on the particle surface, but due to handling in air, the highly reactive surface particles assumedly exhibit oxygen on the surface. Furthermore, a local enrichment of SiO2 due to segregation areas in the particles is not observed 46,47) . Therefore, the high defect density must be a result of lattice mismatches.…”

Section: Electron Microscopy Analysismentioning

confidence: 90%

“…Nanocr ystalline silicon materials synthesized from a microwave plasma process show that the thermal conductivity can be further reduced by minimizing the crystallite size of the used silicon nanoparticles 46) . The results of the measurement are fit using a polynomial function to receive a continuous set of data for further processing.…”

Section: Thermoelectric Properties Of Silicon From Gasphase Synthesismentioning

confidence: 99%

Gas-Phase Synthesis of Nanoscale Silicon as an Economical Route towards Sustainable Energy Technology

Hülser

Schnurre

Wiggers

et al. 2011

KONA

Self Cite

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The silicon age that started in the 60s of the last century has changed the world profoundly, mainly related to the invention and development of microprocessor technology. Meanwhile, the demand for silicon is driven by the photovoltaics industry that consumes about 80% of the high-purity silicon produced worldwide. Independent of the final product, all high-purity silicon has passed through a couple of gas-phase reactions for purification. The most important gaseous species within this production chain are chlorosilanes and monosilane. We will discuss the direct formation of crystalline silicon by homogeneous gas-phase reactions as a direct and highly economical way to produce the required high-purity raw material for silicon solar cells. The direct formation of solid silicon particles from monosilane requires only a fraction of the energy compared to the established Siemens process based on the chemical vapor deposition of silanes. We have developed a method to synthesize nanocrystalline silicon powder using a hot-wall reactor, and the technology was scaled up to the pilot-plant scale. While an economical production strategy is decisive for solar cell production, the structure of the gas-phase product allows for additional, highly promising applications benefiting from the specific properties of the nanoscale particulate material. Both, thermoelectric generators as well as lithiumion batteries benefit from the nanocrystalline structure of the gas-phase product due to high phonon scattering and short diffusion lengths, respectively. First successful examples with regard to these two topics will be discussed. In these fields, silicon finds potential new markets for sustainable energy technology because of its abundant availability and low-cost production.

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“…Finally, in the last decade the properties and the application potential of the resulting materials have increased very much in interest [20,[51][52][53][54][55][56][57][58][59][60].…”

Section: Microwave Plasma Synthesis Of Particulate Matter In the Histmentioning

confidence: 99%

Microwave Plasma Synthesis of Materials—From Physics and Chemistry to Nanoparticles: A Materials Scientist’s Viewpoint

Szabó

Schlabach

2014

Inorganics

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Abstract:In this review, microwave plasma gas-phase synthesis of inorganic materials and material groups is discussed from the application-oriented perspective of a materials scientist: why and how microwave plasmas are applied for the synthesis of materials? First, key players in this research field will be identified, and a brief overview on publication history on this topic is given. The fundamental basics, necessary to understand the processes ongoing in particle synthesis-one of the main applications of microwave plasma processes-and the influence of the relevant experimental parameters on the resulting particles and their properties will be addressed. The benefit of using microwave plasma instead of conventional gas phase processes with respect to chemical reactivity and crystallite nucleation will be reviewed. The criteria, how to choose an appropriate precursor to synthesize a specific material with an intended application is discussed. A tabular overview on all type of materials synthesized in microwave plasmas and other plasma methods will be given, including relevant citations. Finally, property examples of three groups of nanomaterials synthesized with microwave plasma methods, bare Fe 2 O 3 nanoparticles, different core/shell ceramic/organic shell nanoparticles, and Sn-based nanocomposites, will be described exemplarily, comprising perspectives of applications.

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Plasma synthesis of nanostructures for improved thermoelectric properties

Cited by 107 publications

References 67 publications

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Gas-Phase Synthesis of Nanoscale Silicon as an Economical Route towards Sustainable Energy Technology

Microwave Plasma Synthesis of Materials—From Physics and Chemistry to Nanoparticles: A Materials Scientist’s Viewpoint

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