Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System
Four quaternary Zintl phase thermoelectric (TE) materials belonging to the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> (<i>x</i> = 0.02(1), 0.04(1), 0.08(1), 0.15(1)) system were successf...
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2025-01-01
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| author | Daewon Shim Junsu Lee Aziz Ahmed Ji Hee Pi Myung-Ho Choi Kang Min Ok Kyu Hyoung Lee Tae-Soo You |
| author_facet | Daewon Shim Junsu Lee Aziz Ahmed Ji Hee Pi Myung-Ho Choi Kang Min Ok Kyu Hyoung Lee Tae-Soo You |
| author_sort | Daewon Shim |
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| description | Four quaternary Zintl phase thermoelectric (TE) materials belonging to the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> (<i>x</i> = 0.02(1), 0.04(1), 0.08(1), 0.15(1)) system were successfully synthesized using the molten Pb-flux or the conventional high-temperature reaction methods. Their crystal structures were characterized by both powder and single-crystal X-ray diffraction analyses, and all four isotypic title compounds adopted the orthorhombic BaCu<sub>2</sub>S<sub>2</sub>-type (<i>Pnma</i>, <i>Z</i> = 4, Pearson code <i>oP</i>20) structure. The radius ratio criterion, based on the cationic and anionic elements (i.e., <i>r</i><sub>+</sub>/<i>r</i><sub>−</sub>), was successfully verified in the title system, as in our previous reports, where <i>r</i><sub>+</sub>/<i>r</i><sub>−</sub> > 1 for the BaCu<sub>2</sub>S<sub>2</sub>-type structure. A series of density functional theory calculations were performed using a hypothetical model with the idealized compositions of Ba<sub>0.75</sub>Eu<sub>0.25</sub>Zn<sub>2</sub>Sb<sub>2</sub>, and the results were compared with the ternary parental compound BaZn<sub>2</sub>Sb<sub>2</sub> to understand the influence of Eu substituents in the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> system. A similar overall shape of the density of states (DOS) curves and the near-constant DOS values at <i>E</i><sub>F</sub> before and after the cationic substitution suggest only marginal changes in the carrier concentration. Therefore, carrier mobility has a dominant role in rationalizing the observed variations in the electrical transport properties of the title system. Temperature-dependent TE property measurements proved that an increase in the Seebeck coefficient <i>S</i> and a decrease in electrical conductivity <i>σ</i> were observed as the Eu substituents gradually increased in the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> system, although the overall <i>S</i> and <i>σ</i> values were lower than those in the parental compound BaZn<sub>2</sub>Sb<sub>2</sub>. The thermal conductivities of these title compounds were successfully lowered by phonon scattering, but due to the overall smaller electrical transport properties, the observed maximum <i>ZT</i> was 0.49 at 773 K for Ba<sub>0.98(1)</sub>Eu<sub>0.02</sub>Zn<sub>2</sub>Sb<sub>2</sub>. |
| format | Article |
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| language | English |
| publishDate | 2025-01-01 |
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| series | Molecules |
| spelling | doaj-art-c91ceecf3b44409ead5a2ce6cf73e0d42025-01-24T13:43:32ZengMDPI AGMolecules1420-30492025-01-0130231010.3390/molecules30020310Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> SystemDaewon Shim0Junsu Lee1Aziz Ahmed2Ji Hee Pi3Myung-Ho Choi4Kang Min Ok5Kyu Hyoung Lee6Tae-Soo You7Department of Chemistry, Chungbuk National University, Cheongju 28644, Chungbuk, Republic of KoreaDepartment of Chemistry, Chungbuk National University, Cheongju 28644, Chungbuk, Republic of KoreaDepartment of Chemistry, Chungbuk National University, Cheongju 28644, Chungbuk, Republic of KoreaDepartment of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of KoreaDepartment of Chemistry, Sogang University, Seoul 04107, Republic of KoreaDepartment of Chemistry, Sogang University, Seoul 04107, Republic of KoreaDepartment of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of KoreaDepartment of Chemistry, Chungbuk National University, Cheongju 28644, Chungbuk, Republic of KoreaFour quaternary Zintl phase thermoelectric (TE) materials belonging to the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> (<i>x</i> = 0.02(1), 0.04(1), 0.08(1), 0.15(1)) system were successfully synthesized using the molten Pb-flux or the conventional high-temperature reaction methods. Their crystal structures were characterized by both powder and single-crystal X-ray diffraction analyses, and all four isotypic title compounds adopted the orthorhombic BaCu<sub>2</sub>S<sub>2</sub>-type (<i>Pnma</i>, <i>Z</i> = 4, Pearson code <i>oP</i>20) structure. The radius ratio criterion, based on the cationic and anionic elements (i.e., <i>r</i><sub>+</sub>/<i>r</i><sub>−</sub>), was successfully verified in the title system, as in our previous reports, where <i>r</i><sub>+</sub>/<i>r</i><sub>−</sub> > 1 for the BaCu<sub>2</sub>S<sub>2</sub>-type structure. A series of density functional theory calculations were performed using a hypothetical model with the idealized compositions of Ba<sub>0.75</sub>Eu<sub>0.25</sub>Zn<sub>2</sub>Sb<sub>2</sub>, and the results were compared with the ternary parental compound BaZn<sub>2</sub>Sb<sub>2</sub> to understand the influence of Eu substituents in the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> system. A similar overall shape of the density of states (DOS) curves and the near-constant DOS values at <i>E</i><sub>F</sub> before and after the cationic substitution suggest only marginal changes in the carrier concentration. Therefore, carrier mobility has a dominant role in rationalizing the observed variations in the electrical transport properties of the title system. Temperature-dependent TE property measurements proved that an increase in the Seebeck coefficient <i>S</i> and a decrease in electrical conductivity <i>σ</i> were observed as the Eu substituents gradually increased in the Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> system, although the overall <i>S</i> and <i>σ</i> values were lower than those in the parental compound BaZn<sub>2</sub>Sb<sub>2</sub>. The thermal conductivities of these title compounds were successfully lowered by phonon scattering, but due to the overall smaller electrical transport properties, the observed maximum <i>ZT</i> was 0.49 at 773 K for Ba<sub>0.98(1)</sub>Eu<sub>0.02</sub>Zn<sub>2</sub>Sb<sub>2</sub>.https://www.mdpi.com/1420-3049/30/2/310thermoelectric materialZintl phaseDFT calculationsBaCu<sub>2</sub>S<sub>2</sub>-type structureelectronic structurepowder X-ray diffraction |
| spellingShingle | Daewon Shim Junsu Lee Aziz Ahmed Ji Hee Pi Myung-Ho Choi Kang Min Ok Kyu Hyoung Lee Tae-Soo You Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System Molecules thermoelectric material Zintl phase DFT calculations BaCu<sub>2</sub>S<sub>2</sub>-type structure electronic structure powder X-ray diffraction |
| title | Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System |
| title_full | Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System |
| title_fullStr | Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System |
| title_full_unstemmed | Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System |
| title_short | Eu-Substituents-Induced Modifications in the Thermoelectric Properties of the Zintl Phase Ba<sub>1-<i>x</i></sub>Eu<i><sub>x</sub></i>Zn<sub>2</sub>Sb<sub>2</sub> System |
| title_sort | eu substituents induced modifications in the thermoelectric properties of the zintl phase ba sub 1 i x i sub eu i sub x sub i zn sub 2 sub sb sub 2 sub system |
| topic | thermoelectric material Zintl phase DFT calculations BaCu<sub>2</sub>S<sub>2</sub>-type structure electronic structure powder X-ray diffraction |
| url | https://www.mdpi.com/1420-3049/30/2/310 |
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