Thermoelectric properties of icosahedral cluster solids – Metallic-Covalent Bonding Conversion and Weakly Bonded Rigid Heavy Clusters

2005 ◽  
Vol 886 ◽  
Author(s):  
Kaoru Kimura ◽  
Junpei Tamura Okada ◽  
Hongki Kim ◽  
Takehito Hamamatsu ◽  
Tomohiro Nagata ◽  
...  
Keyword(s):  
Figure Of Merit ◽  
Complex Structure ◽  
Covalent Bond ◽  
Covalent Bonding ◽  
Icosahedral Cluster ◽  
Icosahedral Clusters ◽  
Icosahedral Quasicrystals ◽  
Strong Covalent Bond ◽  
P Type ◽  
Rhombohedral Boron

ABSTRACTBoron- or Aluminum-rich icosahedral cluster solids (ICS) consist mainly of B12 or Al12 icosahedral clusters. In the ICS, a slight change of the structure or environment of icosahedral cluster can cause metallic-covalent bonding conversion, which can cause that the electrical conductivity σ and the Seebeck coefficient S can be as high as those of metals and semiconductors, respectively. Five-fold symmetry of the icosahedral cluster does not match with the translational symmetry of a crystal, consequently makes lower thermal conductivity with complex structure. For these reasons, ICS are promising candidates for thermoelectric materials.Using MEM/Rietvelt method, we successfully obtained the clear image of the electron density distribution for alpha-AlReSi approximant crystal. The bond strength distributes widely from weak metallic to strong covalent bond, and the intra-cluster bonds are stronger than the inter-cluster ones. This means that alpha-AlReSi is located at the intermediate state of molecular, metallic- and covalent-bonded solids. Composition dependences of atomic density and quasi-lattice constant for AlPdRe icosahedral quasicrystals show the above situation is the same in the quasicrystals. The thermoelectric figure of merit Z and the effective mass m* of AlPdRe quasicrystals can be increased by strengthening the intra- and weakening the inter-cluster bonds. According to this scenario, Z was improved by a factor of 1.5 by substitution of Ru for Re.In β-rhombohedral boron, several interstitial sites, which have space large enough to accommodate foreign atoms, are known. For the V doped sample, in which V atoms mainly occupy A1 site, the metallic-covalent bonding conversion may occur, σ is increased very much, S is decreased even to negative value and kappa is decreased. The maximum and n-type ZT value is obtained and is approaching to that of B4C, which is considered to have the largest and p-type ZT value in boron-rich ICS.

Interralation Between Hume-Rothery Mechanism, Hybridization and Covalent Bonds in Aluminum- and Boron-based Icrosahedral Approximants and Quasicrystals

2000 ◽  
Vol 643 ◽  
Author(s):  
Kaoru Kimura ◽  
Kazuhiro Kirihara ◽  
Masaaki Fujumori ◽  
Takahiro Nakayama ◽  
Masaki Takata ◽  
...  
Keyword(s):  
Rietveld Method ◽  
Covalent Bonding ◽  
Entropy Method ◽  
Icosahedral Quasicrystal ◽  
Molecular Orbital Calculations ◽  
Covalent Bonds ◽  
Icosahedral Clusters ◽  
Metal Doped ◽  
Electron Energy Loss ◽  
Rhombohedral Boron

AbstractMetallic-covalent bonding conversion in icosahedral clusters of Al and B by small changes of the structure was demonstrated by molecular orbital calculations. According to the electron density distribution obtained using the maximum entropy method and the Rietveld method, the bonding conversion phenomenon occurs even in cluster solids such as some Al- and B-based icosahedral approximant phases (Al12Re, α-AlMnSi, α-rhombohedral boron). The multiple-shell atomic structure, the electrical and optical conductivity are compared for metal doped β-rhombohedral boron and AlLiCu or AlPdRe icosahedral quasicrystal. Photoemission and electron energy loss spectroscopy investigations for V doped β-rhombohedral have been discussed. Conclusions are the following two. It is difficult to distinguish a Hume-Rothery, i.e. structure-induced, pseudogap, and a covalent bonding, i.e. hybridization, pseudogap for materials with a highly symmetric Brillouin zone and a strong potential for valence electrons. Because hybridization is necessary not only for covalent bonds but also for metallic ones, it is better to use the covalent bonding pseudogap than the hybridization pseudogap.

scholarly journals Thermoelectric Properties of Carbon Nanotubes

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4561 ◽  
Author(s):  
Nguyen T. Hung ◽  
Ahmad R. T. Nugraha ◽  
Riichiro Saito
Keyword(s):  
Carbon Nanotubes ◽  
Figure Of Merit ◽  
Waste Heat ◽  
Quantum Confinement Effect ◽  
Electrical Energy ◽  
High Seebeck Coefficient ◽  
Te Material ◽  
P Type ◽  
State Device ◽  
Solid State Device

Thermoelectric (TE) material is a class of materials that can convert heat to electrical energy directly in a solid-state-device without any moving parts and that is environmentally friendly. The study and development of TE materials have grown quickly in the past decade. However, their development goes slowly by the lack of cheap TE materials with high Seebeck coefficient and good electrical conductivity. Carbon nanotubes (CNTs) are particularly attractive as TE materials because of at least three reasons: (1) CNTs possess various band gaps depending on their structure, (2) CNTs represent unique one-dimensional carbon materials which naturally satisfies the conditions of quantum confinement effect to enhance the TE efficiency and (3) CNTs provide us with a platform for developing lightweight and flexible TE devices due to their mechanical properties. The TE power factor is reported to reach 700–1000 W / m K 2 for both p-type and n-type CNTs when purified to contain only doped semiconducting CNT species. Therefore, CNTs are promising for a variety of TE applications in which the heat source is unlimited, such as waste heat or solar heat although their figure of merit Z T is still modest (0.05 at 300 K). In this paper, we review in detail from the basic concept of TE field to the fundamental TE properties of CNTs, as well as their applications. Furthermore, the strategies are discussed to improve the TE properties of CNTs. Finally, we give our perspectives on the tremendous potential of CNTs-based TE materials and composites.

scholarly journals Mechanosynthesis and Thermoelectric Properties of Fe, Zn, and Cd-Doped P-Type Tetrahedrite: Cu12-xMxSb4S13

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3448
Author(s):  
Francisco Arturo López Cota ◽  
José Alonso Díaz-Guillén ◽  
Oscar Juan Dura ◽  
Marco Antonio López de la Torre ◽  
Joelis Rodríguez-Hernández ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Powder Processing ◽  
High Energy ◽  
Secondary Phases ◽  
Ambient Conditions ◽  
Cadmium Sulfate ◽  
Electrical Conductivities ◽  
Compositional Changes ◽  
P Type

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350–400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites’ thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies.

OXYCHALCOGENIDES AS NEW EFFICIENT p-TYPE THERMOELECTRIC MATERIALS

2013 ◽  
Vol 06 (05) ◽  
pp. 1340007 ◽  
Author(s):  
CELINE BARRETEAU ◽  
LIN PAN ◽  
YAN-LING PEI ◽  
LI-DONG ZHAO ◽  
DAVID BERARDAN ◽  
...  
Keyword(s):  
Figure Of Merit ◽  
Parent Compound ◽  
Thermoelectric Figure ◽  
Medium Temperature ◽  
Temperature Range ◽  
The Past ◽  
Thermoelectric Conversion ◽  
New Directions ◽  
Wide Scale ◽  
P Type

During the past two years, we have underlined the great potential of p-type oxychalcogenides, with parent compound BiCuSeO , for thermoelectric applications in the medium temperature range (400–650°C). These materials, which do not contain lead and are less expensive than Te containing materials, exhibit large thermoelectric figure of merit, exceeding 1 in a wide temperature range, mainly due to an intrinsically very low thermal conductivity. This paper summarizes the main chemical and crystallographic features of this system, as well as the thermoelectric properties. It also gives new directions to improve these properties, and discuss the potential of these materials for wide scale applications in thermoelectric conversion system in the medium temperature range.

High-Thermoelectric Figure of Merit Realized in p-Type Half-Heusler Compounds: ZrCoSnxSb1-x

2007 ◽  
Vol 46 (No. 27) ◽  
pp. L673-L675 ◽  
Author(s):  
Takeyuki Sekimoto ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Heusler Compounds ◽  
Thermoelectric Figure ◽  
P Type

Fabrication of Bi-Te Based Thermoelectric Semiconductors by Using Hybrid Powders

2005 ◽  
Vol 297-300 ◽  
pp. 875-880
Author(s):  
Cheol Ho Lim ◽  
Ki Tae Kim ◽  
Yong Hwan Kim ◽  
Dong Choul Cho ◽  
Young Sup Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Single Crystals ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Figure Of Merit ◽  
Bending Strength ◽  
Mixing Ratio ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
P Type

P-type Bi0.5Sb1.5Te3 compounds doped with 3wt% Te were fabricated by spark plasma sintering and their mechanical and thermoelectric properties were investigated. The sintered compounds with the bending strength of more than 50MPa and the figure-of-merit 2.9×10-3/K were obtained by controlling the mixing ratio of large powders (PL) and small powders (PS). Compared with the conventionally prepared single crystal thermoelectric materials, the bending strength was increased up to more than three times and the figure-of-merit Z was similar those of single crystals. It is expected that the mechanical properties could be improved by using hybrid powders without degradation of thermoelectric properties.

Formation of F- and P-Type Icosahedral Quasicrystals in the Zn–Mg–Ho Alloy System*

1998 ◽  
Vol 37 (Part 1, No. 10) ◽  
pp. 5691-5696 ◽  
Author(s):  
Takayuki Shimizu ◽  
Tsutomu Ishimasa
Keyword(s):  
Alloy System ◽  
Icosahedral Quasicrystals ◽  
P Type

The effects of Ge doping on the thermoelectric performance of p-type polycrystalline SnSe

RSC Advances ◽  
2016 ◽  
Vol 6 (115) ◽  
pp. 114825-114829 ◽  
Author(s):  
Tessera Alemneh Wubieneh ◽  
Cheng-Lung Chen ◽  
Pai Chun Wei ◽  
Szu-Yuan Chen ◽  
Yang-Yuan Chen
Keyword(s):  
Figure Of Merit ◽  
Thermoelectric Performance ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
P Type ◽  
Ge Doping

Ge doping enables to enhance the thermoelectric figure of merit of SnSe..

scholarly journals Термоэлектрические свойства нанокомпозитного Bi-=SUB=-0.45-=/SUB=-Sb-=SUB=-1.55-=/SUB=-Te-=SUB=-2.985-=/SUB=- с микрочастицами SiO-=SUB=-2-=/SUB=-

2019 ◽  
Vol 53 (6) ◽  
pp. 751
Author(s):  
А.А. Шабалдин ◽  
П.П. Константинов ◽  
Д.А. Курдюков ◽  
Л.Н. Лукьянова ◽  
А.Ю. Самунин ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Solid Solution ◽  
Electrical Conductivity ◽  
Wide Temperature Range ◽  
Figure Of Merit ◽  
Nanostructured Material ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
P Type

AbstractNanocomposite thermoelectrics based on Bi_0.45Sb_1.55Te_2.985 solid solution of p -type conductivity are fabricated by the hot pressing of nanopowders of this solid solution with the addition of SiO_2 microparticles. Investigations of the thermoelectric properties show that the thermoelectric power of the nanocomposites increases in a wide temperature range of 80–420 K, while the thermal conductivity considerably decreases at 80–320 K, which, despite a decrease in the electrical conductivity, leads to an increase in the thermoelectric efficiency in the nanostructured material without the SiO_2 addition by almost 50% (at 300 K). When adding SiO_2, the efficiency decreases. The initial thermoelectric fabricated without nanostructuring, in which the maximal thermoelectric figure of merit ZT = 1 at 390 K, is most efficient at temperatures above 350 K.

scholarly journals The Optoelectronic Properties of p-Type Cr-Deficient Cu[Cr0.95−xMg0.05]O2 Films Deposited by Reactive Magnetron Sputtering

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2376 ◽  
Author(s):  
Song-Sheng Lin ◽  
Qian Shi ◽  
Ming-Jiang Dai ◽  
Kun-Lun Wang ◽  
Sheng-Chi Chen ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Carrier Mobility ◽  
Figure Of Merit ◽  
Incident Light ◽  
Transparent Conductive Oxide ◽  
Optoelectronic Properties ◽  
Reactive Magnetron Sputtering ◽  
Reactive Magnetron ◽  
Mg Doping ◽  
P Type

CuCrO2 is one of the most promising p-type transparent conductive oxide (TCO) materials. Its electrical properties can be considerably improved by Mg doping. In this work, Cr-deficient CuCrO2 thin films were deposited by reactive magnetron sputtering based on 5 at.% Mg doping. The influence of Cr deficiency on the film’s optoelectronic properties was investigated. As the film’s composition varied, CuO impurity phases appeared in the film. The mixed valency of Cu+/Cu2+ led to an enhancement of the hybridization between the Cu3d and O2p orbitals, which further reduced the localization of the holes by oxygen. As a result, the carrier concentration significantly improved. However, since the impurity phase of CuO introduced more grain boundaries in Cu[Cr0.95−xMg0.05]O2, impeding the transport of the carrier and incident light in the film, the carrier mobility and the film’s transmittance reduced accordingly. In this work, the optimal optoelectronic performance is realized where the film’s composition is Cu[Cr0.78Mg0.05]O2. Its Haacke’s figure of merit is about 1.23 × 10−7 Ω−1.

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