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Issue 37, 2015
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Ba5{V,Nb}12Sb19+x, novel variants of the Ba5Ti12Sb19+x-type: crystal structure and physical properties

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Abstract

The novel compounds Ba5{V,Nb}12Sb19+x, initially found in diffusion zone experiments between Ba-filled skutterudite Ba0.3Co4Sb12 and group V transition metals (V,Nb,Ta), were synthesized via solid state reaction and were characterized by means of X-ray (single crystal and powder) diffraction, electron probe microanalysis (EPMA), and physical (transport and mechanical) properties measurements. Ba5V12Sb19.41 (a = 1.21230(1) nm, space group P[4 with combining overline]3m; RF2 = 0.0189) and Ba5Nb12Sb19.14 (a = 1.24979(2) nm, space group P[4 with combining overline]3m; RF2 = 0.0219) are the first representatives of the Ba5Ti12Sb19+x-type, however, in contrast to the aristotype, the structure of Ba5V12Sb19.41 shows additional atom disorder. Temperature dependent ADPs and specific heat of Ba5V12Sb19.41 confirmed the rattling behaviour of Ba1,2 and Sb7 atoms within the framework built by V and Sb atoms. Electrical resistivity of both compounds show an upturn at low temperature, and a change from p- to n-type conductivity above 300 K in Ba4.9Nb12Sb19.4. As expected from the complex crystal structure and the presence of defects and disorder, the thermal conductivity is suppressed and lattice thermal conductivity of ∼0.43 W m−1 K−1 is near values typical for amorphous systems. Vicker's hardness of (3.8 ± 0.1) GPa (vanadium compound) and (3.5 ± 0.2) GPa (niobium compound) are comparable to Sb-based filled skutterudites. However, the Young's moduli measured by nanoindentation for these compounds EI(Ba4.9V12Sb19.0) = (85 ± 2) GPa and EI(Ba4.9Nb12Sb19.4) = (79 ± 5) GPa are significantly smaller than those of skutterudites, which range from about 130 to 145 GPa.

Graphical abstract: Ba5{V,Nb}12Sb19+x, novel variants of the Ba5Ti12Sb19+x-type: crystal structure and physical properties

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Publication details

The article was received on 09 Jul 2015, accepted on 18 Aug 2015 and first published on 21 Aug 2015


Article type: Paper
DOI: 10.1039/C5CP04000K
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2015,17, 24248-24261
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    Ba5{V,Nb}12Sb19+x, novel variants of the Ba5Ti12Sb19+x-type: crystal structure and physical properties

    F. Failamani, A. Grytsiv, G. Giester, G. Polt, P. Heinrich, H. Michor, E. Bauer, M. Zehetbauer and P. Rogl, Phys. Chem. Chem. Phys., 2015, 17, 24248
    DOI: 10.1039/C5CP04000K

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