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Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants
In this article, we review the characteristic features of icosahedral cluster solids, metallic–covalent bonding conversion (MCBC), and the thermoelectric properties of Al-based icosahedral quasicrystals and approximants. MCBC is clearly distinguishable from and closely related to the well-known meta...
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Taylor & Francis
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5090688/ https://www.ncbi.nlm.nih.gov/pubmed/27877700 http://dx.doi.org/10.1088/1468-6996/15/4/044802 |
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author | Takagiwa, Yoshiki Kimura, Kaoru |
author_facet | Takagiwa, Yoshiki Kimura, Kaoru |
author_sort | Takagiwa, Yoshiki |
collection | PubMed |
description | In this article, we review the characteristic features of icosahedral cluster solids, metallic–covalent bonding conversion (MCBC), and the thermoelectric properties of Al-based icosahedral quasicrystals and approximants. MCBC is clearly distinguishable from and closely related to the well-known metal–insulator transition. This unique bonding conversion has been experimentally verified in 1/1-AlReSi and 1/0-Al(12)Re approximants by the maximum entropy method and Rietveld refinement for powder x-ray diffraction data, and is caused by a central atom inside the icosahedral clusters. This helps to understand pseudogap formation in the vicinity of the Fermi energy and establish a guiding principle for tuning the thermoelectric properties. From the electron density distribution analysis, rigid heavy clusters weakly bonded with glue atoms are observed in the 1/1-AlReSi approximant crystal, whose physical properties are close to icosahedral Al–Pd–TM (TM: Re, Mn) quasicrystals. They are considered to be an intermediate state among the three typical solids: metals, covalently bonded networks (semiconductor), and molecular solids. Using the above picture and detailed effective mass analysis, we propose a guiding principle of weakly bonded rigid heavy clusters to increase the thermoelectric figure of merit (ZT) by optimizing the bond strengths of intra- and inter-icosahedral clusters. Through element substitutions that mainly weaken the inter-cluster bonds, a dramatic increase of ZT from less than 0.01 to 0.26 was achieved. To further increase ZT, materials should form a real gap to obtain a higher Seebeck coefficient. |
format | Online Article Text |
id | pubmed-5090688 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | Taylor & Francis |
record_format | MEDLINE/PubMed |
spelling | pubmed-50906882016-11-22 Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants Takagiwa, Yoshiki Kimura, Kaoru Sci Technol Adv Mater Focus on Complex Metallic Phases In this article, we review the characteristic features of icosahedral cluster solids, metallic–covalent bonding conversion (MCBC), and the thermoelectric properties of Al-based icosahedral quasicrystals and approximants. MCBC is clearly distinguishable from and closely related to the well-known metal–insulator transition. This unique bonding conversion has been experimentally verified in 1/1-AlReSi and 1/0-Al(12)Re approximants by the maximum entropy method and Rietveld refinement for powder x-ray diffraction data, and is caused by a central atom inside the icosahedral clusters. This helps to understand pseudogap formation in the vicinity of the Fermi energy and establish a guiding principle for tuning the thermoelectric properties. From the electron density distribution analysis, rigid heavy clusters weakly bonded with glue atoms are observed in the 1/1-AlReSi approximant crystal, whose physical properties are close to icosahedral Al–Pd–TM (TM: Re, Mn) quasicrystals. They are considered to be an intermediate state among the three typical solids: metals, covalently bonded networks (semiconductor), and molecular solids. Using the above picture and detailed effective mass analysis, we propose a guiding principle of weakly bonded rigid heavy clusters to increase the thermoelectric figure of merit (ZT) by optimizing the bond strengths of intra- and inter-icosahedral clusters. Through element substitutions that mainly weaken the inter-cluster bonds, a dramatic increase of ZT from less than 0.01 to 0.26 was achieved. To further increase ZT, materials should form a real gap to obtain a higher Seebeck coefficient. Taylor & Francis 2014-07-02 /pmc/articles/PMC5090688/ /pubmed/27877700 http://dx.doi.org/10.1088/1468-6996/15/4/044802 Text en © 2014 National Institute for Materials Science http://creativecommons.org/licenses/by-nc-sa/3.0/ Content from this work may be used under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 licence (http://creativecommons.org/licenses/by-nc-sa/3.0) . Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
spellingShingle | Focus on Complex Metallic Phases Takagiwa, Yoshiki Kimura, Kaoru Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title | Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title_full | Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title_fullStr | Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title_full_unstemmed | Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title_short | Metallic–covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants |
title_sort | metallic–covalent bonding conversion and thermoelectric properties of al-based icosahedral quasicrystals and approximants |
topic | Focus on Complex Metallic Phases |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5090688/ https://www.ncbi.nlm.nih.gov/pubmed/27877700 http://dx.doi.org/10.1088/1468-6996/15/4/044802 |
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