*Pressemitteilung* ,,Mit winzigen Nanopartikeln zu besserem Ladungstransport (Nr. 75/2021)" Von Sepideh Izadi und Prof. Dr. Gabi Schierning Zur Pressemitteilung
Lauritz Ule Schnatmann
ERC Consolidator Grant 2019
Funding period: 01.06.2020-31.05.2025
Ever since the discovery of topological surface states in three-dimensional (3D) topological insulators (TI), this fascinating physics has thrilled scientists. While arguable the transport properties of 3D TIs are of utmost importance for potential applications, they are extremely difficult to characterize, yet utilize for devices. The reason is that transport in those materials is always dominated by bulk carriers. Within this proposed research project, I will overcome the problem of bulk carrier domination conceptually by a nanoparticle-based materials’ design of interrupted early stage sintering. By this interrupted early stage sintering approach, I compact 3D TI nanoparticles at mild temperature and low pressure. The obtained highly porous macroscopic sample features a carrier density of the surface states in the order of 1018 cm-3, hence in a comparable order of magnitude as the bulk carrier density. Further, the interruptedly sintered nanoparticles impose energetic barriers for the transport of bulk carriers (hopping transport), while the connected surfaces of the nanoparticles provide a 3D percolation path for surface carriers. Within the preliminary work, my group tuned interruptedly sintered nanoparticles into a transport regime completely dominated by the surface states.
Within this project, nanoparticle-based macroscopic 3D TI materials will be developed towards test structures for devices. Their properties will be tailored by the nanoparticle synthesis (Objective 1) and the materials processing of interrupted early stage sintering (Objective 2). This is complemented by an in-depth characterization of the transport as well as spectroscopic properties and data modelling (Objective 3). My group will use this know-how for the fabrication of test devices (Objective 4). This combination will provide the first macroscopic quantum transport devices that utilize the unique electronic properties of surface states, overcoming the problem of bulk carrier domination.
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme. Grant agreement No. 863823.
Key benefits of compacted nanoparticle arrays
For the internet of things (IoT) in general and medical sensors in particular, low power wireless data transmitters are required. Up to date, most of such transmitters require batteries or inefficient radio frequency (RF) harvesting.
In THAWIT, we want to investigate and demonstrate the first wireless data transmitter, which can be supplied by means of compact integrated thermoelectric harvesting. To allow supply-autarkic operation, we have to meet the following challenges. The power consumption of the transmitter must be massively reduced. Moreover, the power density of the thermoelectric devices must be increased. A major challenge is the capability for integration on silicon limiting the possible material compositions. We want to develop silicon-compatible harvesting elements with a power density beyond 10 μW/mm2 at a moderate temperature difference of 7 K. To meet this challenge, we rigorously optimise the geometry and material compositions. A high thermoelectric leg height is necessary for high output power density, affecting the choice of the photoresist and deposition parameters of the thermoelectric material. A new process for the p-type thermoelectric leg is researched to reduce the thermal conductivity. In addition, we develop a silicon-compatible micro-supercapacitor serving as energy buffer. To enable compatibility with the fabrication technology and equipment at IFW, we realize it by a high-performance all-solid-state interdigital in-plane micro-supercapacitor. It is based on photo-lithographically patterned sputtered electrodes and a solid electrolyte.
Considering energy saving losses and component areas of 2 mm2, the CMOS transmitter must operate with a dc power of around 10 μW. To enable such an ultra-low dc power, we study direct modulated oscillators with aggressive duty-cycling of around 0.1 %, fast ramp-up and miniaturized leakage in the sleep phases. In addition to impedance-matched antennas requiring buffer amplifiers, we consider also inductive antennas which can be directly incorporated in the LC-resonator of the oscillator. A textile-compatible woven or printed antenna is designed for the demonstrator. The demonstrator shall operate according to the medical implant communication service (MICS). The final goal is to show data transmission around 400 MHz with a data rate of 1-10 kb/s for distances of up to 1 meter. THAWIT combines the complementary competences of Gabi Schierning, IFW, in the area of thermoelectric devices, and Frank Ellinger, TUD regarding low power integrated RF circuits.
This project has received funding from the Deutsche Forschungsgemeinschaft (DFG) under grand number SCHI 1010/12-1.
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Towards tellurium-free thermoelectric modules for power generation from low-grade heat.
Ying P, He R, Mao J, Zhang Q, Reith H, Sui J, Ren Z, Nielsch K, Schierning G (2021)
Nature communications 12(1): 1121
"Thermoelectric technology converts heat into electricity directly and is a promising source of clean electricity. Commercial thermoelectric modules have relied on Bi2Te3-based compounds because of their unparalleled thermoelectric properties at temperatures associated with low-grade heat (<550 K). However, the scarcity of elemental Te greatly limits the applicability of such modules. Here we report the performance of thermoelectric modules assembled from Bi2Te3-substitute compounds, including p-type MgAgSb and n-type Mg3(Sb,Bi)2, by using a simple, versatile, and thus scalable processing routine. For a temperature difference of ~250 K, whereas a single-stage module displayed a conversion efficiency of ~6.5%, a module using segmented n-type legs displayed a record efficiency of ~7.0% that is comparable to the state-of-the-art Bi2Te3-based thermoelectric modules. Our work demonstrates the feasibility and scalability of high-performance thermoelectric modules based on sustainable elements for recovering low-grade heat."
Influence of Nanoparticle Processing on the Thermoelectric Properties of (BixSb1-X)(2)Te-3 Ternary Alloys
Salloum S, Bendt G, Heidelmann M, Loza K, Bayesteh S, Sepideh Izadi M, Kawulok P, He R, Schlorb H, Perez N, Reith H, et al. (2021)
ChemistryOpen 10(2): 189-198.
“The synthesis of phase-pure ternary solutions of tetradymite-type materials (BixSb1-x)(2)Te-3 (x=0.25; 0.50; 0.75) in an ionic liquid approach has been carried out. The nanoparticles are characterized by means of energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy. In addition, the role of different processing approaches on the thermoelectric properties - Seebeck coefficient as well as electrical and thermal conductivity - is demonstrated.“
|2002||Material Science and Engineering||University of Erlangen-Nürnberg||Dipl. Ing.|
|2005||Material Science and Engineering||University of Erlangen-Nürnberg||Dr.Ing.|
|2016||Materials for Electrical Engineering||University of Duisburg-Essen||Dr. Ing. habil.|
W2 TT W3 Professor for experimental physics, department of physics, University of Bielefeld, Germany
Head of group „Thermoelectric materials and devices“, in the Institute for Metallic Materials, Leibniz-Institute for solid state and materials science Dresden e.V. (IFW-Dresden), Germany, with director Prof. K. Nielsch
Leader of an independent young researcher group in the department of electrical engineering, University of Duisburg-Essen, Germany
Research assistant in the department of electrical engineering, University of Duisburg-Essen, Germany, with Prof. R. Schmechel
Research assistant in the Institute for Nanotechnology, Karlsruhe Institute of Technology (KIT), Germany, with director Prof. H. Hahn
|2005||Employee at Siemens Medical Solutions, Forchheim|
Research assistant in the department of materials science, Darmstadt Technical University, Germany, with Prof. H. von Seggern
Research internship in the school of chemical and physical sciences, Victoria University of Wellington, New Zealand, with Prof. A. Edgar
Research assistant in the department of materials science and engineering, University of Erlangen-Nürnberg, Germany, with Prof. A. Winnacker