Artificially nanostructured n-type SiGe bulk thermoelectrics through plasma enhanced growth of alloy nanoparticles from the gas phase

Stein, Niklas; Petermann, Nils; Theissmann, Ralf; Schierning, Gabi; Schmechel, Roland; Wiggers, Hartmut

doi:10.1557/jmr.2011.117

Cited by 24 publications

(45 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The nanoparticles are crystalline (inset of Figure 12 b) and weakly agglomerated and typically show no crystal facets, due to kinetic control of the particle formation process. A subsequent current assisted sintering at temperatures around 1000 ° C results in an alloyed nanocrystalline bulk with average crystallite size around 30 nm and typical densities between 95% and 98% of the respective single crystal; Figure 12 at 1000 ° C. [ 101 ] Most likely, this type of materials synthesis will be also applied soon for other classed of nanograined thermoelectric materials.…”

Section: Bulkmaterialsmentioning

confidence: 99%

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Nielsch

Bachmann

Kimling

et al. 2011

Advanced Energy Materials

221

138

View full text Add to dashboard Cite

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.

show abstract

Section: Bulkmaterialsmentioning

confidence: 99%

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Nielsch

Bachmann

Kimling

et al. 2011

Advanced Energy Materials

221

138

View full text Add to dashboard Cite

show abstract

“…The composition of the latter material is typical for thermoelectric applications. 25,26 Using HF, the laser-sintered films were released from the quartz substrate and transferred onto a Ge wafer, acting as a heat sink support. To suspend the laser-sintered film, a trench had been etched into the Ge wafer before film transfer.…”

mentioning

confidence: 99%

Thermal conductivity of mesoporous films measured by Raman spectroscopy

Stoib

Filser

Petermann

et al. 2014

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…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: 98%

“…The mean free path for phonons in highly doped silicon is a few tens of nanometers, while that for electrons is below 10 nm 58) . Thus, nanostructuring of silicon is an appropriate tool for designing thermoelectric generators with enhanced properties 33) , and alloying of the nanoparticles might give another degree of freedom 47,[59][60][61] . For this purpose, gas-phase synthesized silicon nanopowder doped with 1% of boron was spark-plasma-sintered for 180 s at a temperature of 1100 C into almost dense pellets.…”

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

View full text Add to dashboard Cite

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.

show abstract

Artificially nanostructured n-type SiGe bulk thermoelectrics through plasma enhanced growth of alloy nanoparticles from the gas phase

Abstract: Abstract

Cited by 24 publications

References 21 publications

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Thermoelectric Nanostructures: From Physical Model Systems towards Nanograined Composites

Thermal conductivity of mesoporous films measured by Raman spectroscopy

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

Contact Info

Product

Resources

About