Thermoelectric properties of lead chalcogenide core-shell nanostructures

We present the full thermoelectric characterization of nanostructured bulk PbTe and PbTe-PbSe samples fabricated from colloidal core-shell nanoparticles followed by spark plasma sintering. An unusually large thermopower is found in both materials, and the possibility of energy filtering as opposed to grain boundary scattering as an explanation is discussed. A decreased Debye temperature and an increased molar specific heat are in accordance with recent predictions for nanostructured materials. On the basis of these results we propose suitable core-shell material combinations for future thermoelectric materials of large electric conductivities in combination with an increased thermopower by energy filtering.Comment: 12 pages, 8 figure

High-performance shape-engineerable thermoelectric painting

Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm(-2). This approach paves the way to designing materials and devices that can be easily transferred to other applications.ope

Pbca-Type In2O3: the high-pressure post-corundum phase at room temperature

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp5061599High-pressure powder X-ray diffraction and Raman scattering measurements in cubic bixbyite-type indium oxide (c-In2O3) have been performed at room temperature. On increasing pressure c-In2O3 undergoes a transition to the Rh2O3-II structure but on decreasing pressure Rh2O3-II-type In2O3 undergoes a transition to a previously unknown phase with Pbca space group which is isostructural to Rh2O3-III. On further decrease of pressure, we observed a phase transition to the metastable corundum-type In2O3 near room conditions. Recompression of the metastable corundum-type In2O3 at room temperature leads to a transition to the Rh2O3-III phase, thus showing that the Rh2O3-III phase is the post-corundum phase at room temperature. Our results are supported by theoretical ab initio calculations. Furthermore, they show that the Rh2O3-III phase could be present in other sesquioxides, thus prompting to a revision of the pressure-temperature phase diagrams of sesquioxidesFinancial support by the Spanish MEC under Grant No. MAT2010-21270-C04-01/03/04, MAT2013-46649-C4-1/2/3-P, by MALTA Consolider Ingenio 2010 project (CSD2007-00045) and by Generalitat Valenciana (GVA-ACOMP-2013-012). Red Espanola de Supercomputacion (RES) and ALBA Synchrotron Light Source are also acknowledged. B.G.-D. and J.A.S. acknowledge financial support through the FPI program and Juan de la Cierva fellowship, respectively. We also thank J. L. Jorda for fruitful discussions. A.L.J.P. acknowledges financial support through Brazilian CNPq. A.S. expresses thanks to FEDER Grant UNLV10-3E-1253 for financial support.García-Domene, B.; Sans Tresserras, JÁ.; Gomis, O.; Manjón Herrera, FJ.; Ortiz, HM.; Errandonea, D.; Santamaría Pérez, D.... (2014). Pbca-Type In2O3: the high-pressure post-corundum phase at room temperature. Journal of Physical Chemistry C. 118(35):20545-20552. https://doi.org/10.1021/jp5061599S20545205521183

Thermal Transport in Micro- and Nanoscale Systems

Small-scale (micro-/nanoscale) heat transfer has broad and exciting range of applications. Heat transfer at small scale quite naturally is influenced – sometimes dramatically – with high surface area-to-volume ratios. This in effect means that heat transfer in small-scale devices and systems is influenced by surface treatment and surface morphology. Importantly, interfacial dynamic effects are at least non-negligible, and there is a strong potential to engineer the performance of such devices using the progress in micro- and nanomanufacturing technologies. With this motivation, the emphasis here is on heat conduction and convection. The chapter starts with a broad introduction to Boltzmann transport equation which captures the physics of small-scale heat transport, while also outlining the differences between small-scale transport and classical macroscale heat transport. Among applications, examples are thermoelectric and thermal interface materials where micro- and nanofabrication have led to impressive figure of merits and thermal management performance. Basic of phonon transport and its manipulation through nanostructuring materials are discussed in detail. Small-scale single-phase convection and the crucial role it has played in developing the thermal management solutions for the next generation of electronics and energy-harvesting devices are discussed as the next topic. Features of microcooling platforms and physics of optimized thermal transport using microchannel manifold heat sinks are discussed in detail along with a discussion of how such systems also facilitate use of low-grade, waste heat from data centers and photovoltaic modules. Phase change process and their control using surface micro-/nanostructure are discussed next. Among the feature considered, the first are microscale heat pipes where capillary effects play an important role. Next the role of nanostructures in controlling nucleation and mobility of the discrete phase in two-phase processes, such as boiling, condensation, and icing is explained in great detail. Special emphasis is placed on the limitations of current surface and device manufacture technologies while also outlining the potential ways to overcome them. Lastly, the chapter is concluded with a summary and perspective on future trends and, more importantly, the opportunities for new research and applications in this exciting field

Anomalous Electronic Transport in Dual-Nanostructured Lead Telluride

U.S. Department of Energy, Office of Basic Energy Science [DE-SC0001054]; NSF-NSEC; NSF-MRSEC; Keck Foundation; State of Illinois; Northwestern University; SRFDP [20090121120028]; NSF of Fujian Province, China [2009J01015]The Pb- and Sb-dual nanostructured PbTe system exhibits anomalous electronic transport behavior wherein the carrier mobility first increases and then decreases with increase in temperature. By combining in situ transmission electron microscopy observations and theoretical calculations based on energy filtering of charge carriers, we propose a plausible mechanism of charge transport based on interphase potential that is mediated by interdiffusion between coexisting Pb and Sb precipitates. These findings promise new strategies to enhance thermoelectric figure of merit via dual and multinanostructuring of miscible precipitates

Role of Self-Organization, Nanostructuring, and Lattice Strain on Phonon Transport in NaPb18-xSnxBiTe20 Thermoelectric Materials

Office of Naval Research [N00014-08-1-0613]; NSF-NSEC; NSF-MRSEC; Keck Foundation; State of Illinois; Northwestern University; DOE Office of Science [DEAC02-98CH10886]The composition and microstructure of five thermoelectric materials, PbTe, SnTe, Pb0.65Sn0.35Te and NaPb18-xSnxBiTe20 (x = 5, 9), were investigated by advanced transmission electron microcopy. We confirm that the pure PbTe, SnTe, and Pb0.65Sn0.35Te have a uniform crystalline structure and homogeneous compositions without any nanoscale inclusions. On the other hand, the nominal NaPb9Sn9BiTe20 phase contains extensive inhomogeneities and nanostructures with size distribution of 3-7 nm. We find that the chemical architecture of the NaPb13Sn5BiTe20 member of the series to be more complex; besides nanoscale precipitates, self-organized lamellar structures are present which were identified as PbTe and SnTe by composition analysis and transmission electron microscopy image simulations. Density functional theory calculations suggest that the arrangement of the lamellar structures conforms to the lowest total energy configuration. Geometric-phase analyses revealed large distributed elastic strain around the nanoscale inclusions and lamellar structures. We propose that interface-induced elastic perturbations in the matrix play a decisive role in affecting the phonon-propagation pathways. The interfaces further enhance phonon scattering which, in turn, reduces the lattice thermal conductivity in these systems that directly results directly in improvement in the thermoelectric figure of merit

On the Origin of Increased Phonon Scattering in Nanostructured PbTe Based Thermoelectric Materials

Office of Naval Research; Xiamen University of China; Specialized Research Fund [20090121120028]; Natural Science Foundation of Fujian Province, China [2009J01015]; DOE Office of Science [DEAC02-98CH10886]We have investigated the possible mechanisms of phonon scattering by nanostructures and defects in PbTe-X (X = 2% Sb, Bi, or Pb) thermoelectric materials systems. We find that among these three compositions, PbTe-2% Sb has the lowest lattice thermal conductivity and exhibits a larger strain and notably more misfit dislocations at the precipitate/PbTe interfaces than the other two compositions. In the PbTe-Bi 2% sample, we infer some weaker phonon scattering BiTe precipitates, in addition to the abundant Bi nanostructures. In the PbTe-Pb 2% sample, we also find that pure Pb nanoparticles exhibit stronger phonon scattering than nanostructures with Te vacancies. Within the accepted error range, the theoretical calculations of the lattice thermal conductivity in the three systems are in close agreement with the experimental measurements, highlighting the important role of misfit dislocations, nanoscale particles, and associated interfacial elastic strain play in phonon scattering. We further propose that such particle-induced local elastic perturbations interfere with the phonon propagation pathway, thereby contributing to further reduction in lattice thermal conductivity, and consequently can enhance the overall thermoelectric figure of merit