Nanoengineering thermoelectrics for 21st century: Energy harvesting and other trends in the field (original) (raw)
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Nanoengineering Thermoelectrics for 21st century applications
2012
In the beginning of the 21st century, the world is facing the major challenge of finding energy sources to satisfy the ever-increasing energy consumption while preserving the environment. In the race to search alternative energy sources, thermoelectric generators are called to play their role in the improvement of the efficiency of the actual energy system by harvesting nowadays wasted heat. This review deals with the novel aspects of nano-structuring of thermoelectric materials, from the so called 3D nanobulk materials down to the incorporation of 0D quantum dots in thermoelectric structures. The improvement in the efficiency of nanoengineering thermoelectrics benefits mainly from the reduction in the thermal conductivity. Other promising trends in thermoelectricity are also reviewed, such as, novel nanostructures, trending materials (polymers, thermionic materials or Zintl phases), spin caloritronics, thermoelectricity in atomic and molecular junctions, or recent developments in theoretical calculations. Finally the review ends with a brief review on recent thermoelectric devices.
Nanostructured thermoelectric materials: Current research and future challenge
Progress in Natural Science: Materials International, 2012
The field of thermoelectrics has long been recognized as a potentially transformative power generation technology and the field is now growing steadily due to their ability to convert heat directly into electricity and to develop cost-effective, pollution-free forms of energy conversion. Of various types of thermoelectric materials, nanostructured materials have shown the most promise for commercial use because of their extraordinary thermoelectric performances. This article aims to summarize the present progress of nanostructured thermoelectrics and intends to understand and explain the underpinnings of the innovative breakthroughs in the last decade or so. We believed that recent achievements will augur the possibility for thermoelectric power generation and cooling, and discuss several future directions which could lead to new exciting next generation of nanostructured thermoelectrics.
Journal of Electronic Materials, 2018
This review is focused on state-of-the-art thermoelectric materials (or thermoelements), from which the thermoelements with the highest figures of merit (z) along with the those having the greatest research interest and findings were surveyed and analyzed. These were in addition to the statistical analyses made in this review for categorizing z achievement ranges for all types of thermoelements. Almost 56% of positive thermoelements and 39.6% of negative thermoelements were discovered from 1950 to 2017, and a total of 62.2% of thermoelement research findings were reported in 2010-2017. Furthermore, nearly 47.65% of the discovered thermoelements preserved z in the range of 1-4.99 9 10 À3 K À1 , and only about 2.52% possessed less than 9.9 9 10 À6 K À1. Chalcogenide was the major type of thermoelement studied to date, with overall representation of 37.2%. Nearly 68.9% of chalcogenide thermoelements were capable of reach 1-4.99 9 10 À3 K À1 , while 53% of metal oxide thermoelements ranged within 0.1-0.499 9 10 À3 K À1. Nanostructure thermoelements achieved the highest z of 47 9 10 À3 K À1 and 17 9 10 À3 K À1 at 300 K, for Bi 2 Te 3 quantum wires and Bi 2 Te 3 quantum wells, respectively. Correspondingly, hybrid and conducting polymer thermoelements also reached z as high as 16 9 10 À3 K À1 at 300 K for positive thermoelement: nano-Ag/regioregular poly(3-octylthiophene-2,5-diyl) and negative thermoelement: graphdiyne.
Advances in thermoelectric materials research: Looking back and moving forward
Science (New York, N.Y.), 2017
High-performance thermoelectric materials lie at the heart of thermoelectrics, the simplest technology applicable to direct thermal-to-electrical energy conversion. In its recent 60-year history, the field of thermoelectric materials research has stalled several times, but each time it was rejuvenated by new paradigms. This article reviews several potentially paradigm-changing mechanisms enabled by defects, size effects, critical phenomena, anharmonicity, and the spin degree of freedom. These mechanisms decouple the otherwise adversely interdependent physical quantities toward higher material performance. We also briefly discuss a number of promising materials, advanced material synthesis and preparation techniques, and new opportunities. The renewable energy landscape will be reshaped if the current trend in thermoelectric materials research is sustained into the foreseeable future.
New directions for nanoscale thermoelectric materials research
2005
Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena with both bulk samples containing nanoscale constituents and nanoscale materials exhibiting enhanced thermoelectric performance in their own right. Prior theoretical and experimental proof of principle studies on isolated quantum well and quantum wire samples have now evolved into studies on bulk samples containing nanostructured constituents. In this review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications. A review of some of the results obtained to date are presented.
Review of Recent Progresses in Thermoelectric Materials
Advances in Engineering Materials, 2021
Thermoelectric (TE) technology facilitates the direct conversion of heat into electricity and vice versa. Thermoelectric materials attract researchers since they facilitate a promising green energy solution in the form of solid-state cooling and power generation. However, the low energy conversion efficiency restricts the use of TE materials in real-world applications. Developing highly efficient thermoelectric materials is necessary to benefit the environment as well as the economy. The performance of a particular TE material is generally evaluated by the dimensionless figure of merit (ZT). Recent years have witnessed progress with new techniques in maximizing the ZT values of various thermoelectric materials. In this review, we summarize recent development in thermoelectric materials for a specific temperature range, which has been developed to improve their maximum ZT value up to 95% at the same temperature.
Efficiency of Energy Conversion in Thermoelectric Nanojunctions
Using first-principles approaches, this study investigated the efficiency of energy conversion in nanojunctions, described by the thermoelectric figure of merit ZT. We obtained the qualitative and quantitative descriptions for the dependence of ZT on temperatures and lengths. A characteristic temperature: T0 = p β/γ(l) was observed. When T ≪ T0, ZT ∝ T 2. When T ≫ T0, ZT tends to a saturation value. The dependence of ZT on the wire length for the metallic atomic chains is opposite to that for the insulating molecules: for aluminum atomic (conducting) wires, the saturation value of ZT increases as the length increases; while for alkanethiol (insulating) chains, the saturation value of ZT decreases as the length increases. ZT can also be enhanced by choosing low-elasticity bridging materials or creating poor thermal contacts in nanojunctions.
Thermoelectric Materials: Fundamental, Applications and Challenges
Vietnam Journal of Science and Technology, 2018
Energy and the environment are popular themes in the 21st century because both are closely interlinked. The current technologies are focusing on finding new, clean, safe and renewable energy sources for a better environment. Thermoelectric (TE) materials are able to generate electricity when applied a temperature different at a junction of two dissimilar materials. This is a promising technology to directly convert waste heat into electricity without any gas emission, thus providing one of the most clean and safe energy. However, the applications of TE devices are still limited due to its low energy conversion efficiency and high material cost. As a result, researches in TE materials are mainly focusing on the improving of efficiency and developing cheap materials. In this paper, the fundamental, challenges and applications of thermoelectric materials were reviewed. In addition, currently research in thermoelectric materials and improving their efficiency will also be reviewed.
A new class of doped nanobulk high-figure-of-merit thermoelectrics by scalable bottom-up assembly
Nature Materials, 2012
Materials and methods Nanoplate synthesis: Thioglycolic acid (CH 2 COOHSH, 95%), anhydrous bismuth chloride (BiCl 3), antimony chloride (SbCl 3), 1,5-pentanediol (95%), technical grade trioctylphosphine (TOP), 200-mesh tellurium shots and 100-mesh selenium shots obtained from Sigma Aldrich were used without further purification. In a typical small-scale synthesis, we added ~0.08 mmol of tellurium or selenium to 2-5 mL TOP and heated in a multimode 1250 W domestic microwave oven for 90-120 s to obtain a faint yellow TOP-chalcogen complex. We added ~0.04 mmol of BiCl 3 or SbCl 3 to 2.5-10 ml of 1-5 pentanediol followed by sonication for 5 min to obtain a bismuth chloride or antimony chloride solution. The bismuth chloride solution turns yellow upon addition of 100-350 µL of thioglycolic acid (TGA) due to thioligated bismuth complex formation. The solutions with TOP-chalcogen and thioligated bismuth (or antimony) were mixed and exposed to microwaves for ~30-60 s in a multi-mode domestic microwave oven or a single-mode variable power 300 W CEM microwave oven equipped with an IR sensor for temperature control. The whole procedure is simple and quick: it can be completed in ~15 min. The nanoplates were cleaned by repeated centrifugation and sonication with isopropanol and acetone, and left to dry under ambient conditions, to obtain powders consisting of single-crystal nanoparticles. Pellet fabrication: We fabricated pellets from dried nanoplate aggregates through cold-compaction using a hydraulic press. The ~60-70 % dense "green" pellets were sintered in a 10-7 Torr vacuum at 300-400 °C for 60-120 minutes to obtain up to ~92±3% density measured by the Archimedes method, i.e., from the pellet weight in air and in a liquid of known density. For thermoelectric measurements, we used 6-mm-diameter cylindrical pellets with 2-5 mm thickness obtained by cutting and polishing using standard metallography techniques. We note that all properties reported in the paper are actual experimental measured values obtained from the nanobulk materials as a whole. While models assuming a linear pore fraction reveal a higher σ (e.g., up to 10%) for the non-porous portion of the pellet (e.g., with A new class of doped nanobulk high-figure-of merit thermoelectrics by scalable bottom-up assembly SUPPLEMENTARY INFORMATION