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Author |
Verchenko, V.Y.; Wei, Z.; Tsirlin, A.A.; Callaert, C.; Jesche, A.; Hadermann, J.; Dikarev, E.V.; Shevelkov, A.V. |
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Title |
Crystal growth of the Nowotny chimney ladder phase Fe2Ge3 : exploring new Fe-based narrow-gap semiconductor with promising thermoelectric performance |
Type |
A1 Journal article |
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Year  |
2017 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem Mater |
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Volume |
29 |
Issue |
23 |
Pages |
9954-9963 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
<script type='text/javascript'>document.write(unpmarked('A new synthetic approach based on chemical transport reactions has been introduced to obtain the Nowotny chimney ladder phase Fe2Ge3 in the form of single crystals and polycrystalline powders. The single crystals possess the stoichiometric composition and the commensurate chimney ladder structure of the Ru2Sn3 type in contrast to the polycrystalline samples that are characterized by a complex microstructure. In compliance with the 18-n electron counting rule formulated for T-E intermetallics, electronic structure calculations reveal a narrow-gap semiconducting behavior of Fe2Ge3 favorable for high thermoelectric performance. Measurements of transport and thermoelectric properties performed on the polycrystalline samples confirm the formation of a narrow band gap of similar to 30 meV and reveal high absolute values of the Seebeck coefficient at elevated temperatures. Low glass-like thermal conductivity is observed in a wide temperature range that might be caused by the underlying complex microstructure.')); |
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Publisher |
American Chemical Society |
Place of Publication |
Washington, D.C |
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Wos |
000418206600013 |
Publication Date |
2017-11-14 |
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ISSN |
0897-4756 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
9.466 |
Times cited |
11 |
Open Access |
OpenAccess |
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Notes |
; The authors thank Dr. Sergey Kazakov and Oleg Tyablikov for their help with the PXRD experiments. V.Y.V. appreciates the help of Dr. Sergey Dorofeev in provision and handling of the Mo(CO)<INF>6</INF> reagent. The work is supported by the Russian Science Foundation, Grant No. 17-13-01033. V.Y.V. appreciates the support from the European Regional Development Fund, Project No. TK134. A.A.T. acknowledges financial support by the Federal Ministry for Education and Research under the Sofia Kovalevskaya Award of the Alexander von Humboldt Foundation. E.V.D. thanks the National Science Foundation, Grant No. CHE-1152441. C.C. acknowledges the support from the University of Antwerp through the BOF Grant No. 31445. ; |
Approved |
Most recent IF: 9.466 |
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Call Number |
UA @ lucian @ c:irua:148531 |
Serial |
4869 |
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Author |
Lieberman, C.M.; Filatov, A.S.; Wei, Z.; Rogachev, A.Y.; Abakumov, A.M.; Dikarev, E.V. |
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Title |
Mixed-valent, heteroleptic homometallic diketonates as templates for the design of volatile heterometallic precursors |
Type |
A1 Journal article |
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Year |
2015 |
Publication |
Chemical science |
Abbreviated Journal |
Chem Sci |
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Volume |
6 |
Issue |
6 |
Pages |
2835-2842 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
A novel series of mixed-valent, heteroleptic transition metal diketonates that can be utilized as prospective single-source precursors for the low-temperature preparation of oxide materials are reported. The first mixed-valent iron beta-diketonates with different Fe-III/Fe-II ratios have been synthesized by applying the mixed-ligand approach. Based on nearly quantitative reaction yields and analysis of iron-oxygen bonds, these compounds were formulated as [Fe-III(acac)(3)][Fe-II(hfac)(2)] (1) and [Fe-II(hfac)(2)][Fe-III(acac)(3)][Fe-II(hfac)(2)] (2). In the above heteroleptic complexes, the Lewis acidic, coordinatively unsaturated Fe-II centers chelated by two hfac (hexafluoroacetylacetonate) ligands with electron-withdrawing substituents maintain bridging interactions with oxygen atoms of electron-donating acac (acetylacetonate) groups that chelate the neighboring Fe-III atoms. Switching the ligands on Fe-III and Fe-II atoms in starting reagents resulted in the instant ligand exchange between iron centers and in yet another polynuclear homometallic diketonate [Fe-II(hfac)(2)][Fe-III(acac)(2)(hfac)][Fe-II(hfac)(2)] (3) that adheres to the same bonding pattern as in complexes 1 and 2. The proposed synthetic methodology has been extended to design heterometallic diketonates with different M : M' ratios. Homometallic parent molecules have been used as templates to obtain heterometallic mixed-valent [Fe-III(acac)(3)][Mn-II(hfac)(2)] (4) and [Ni-II(hfac)(2)] – [Fe-III(acac)(3)][Ni-II(hfac)(2)] (5) complexes. The combination of two different diketonate ligands with electron-donating and electron-withdrawing substituents was found to be crucial for maintaining the above mixed-valent heterometallic assemblies. Theoretical investigation of two possible “isomers”, [Fe-III(acac)(3)][Mn-II(hfac)(2)] (4) and [Mn-III(acac)(3)][Fe-II(hfac)(2)] (40) provided an additional support for the metal site assignment giving a preference of 9.78 kcal mol(-1) for the molecule 4. Heterometallic complexes obtained in the course of this study have been found to act as effective single-source precursors for the synthesis of mixed-transition metal oxide materials MxM2-xO3 and MxMi-xO. The title highly volatile precursors can be used for the low-temperature preparation of both amorphous and crystalline heterometallic oxides in the form of thin films or nanosized particles that are known to operate as efficient catalysts in oxygen evolution reaction. |
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Publisher |
Royal Society of Chemistry |
Place of Publication |
Cambridge |
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Wos |
000353223100021 |
Publication Date |
2015-02-25 |
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Edition |
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ISSN |
2041-6520;2041-6539; |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
8.668 |
Times cited |
13 |
Open Access |
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Notes |
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Approved |
Most recent IF: 8.668; 2015 IF: 9.211 |
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Call Number |
c:irua:126031 |
Serial |
2092 |
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