Gallium substitutions as a means to stabilize alkaline-earth and rare-earth metal pnictides with the cubic Th{sub 3}P{sub 4} type: Synthesis and structure of A{sub 7}Ga{sub 2}Sb{sub 6} (A=Sr, Ba, Eu)
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 (United States)
Three new compounds-Sr{sub 7.04(2)}Ga{sub 1.94(2)}Sb{sub 6}, Ba{sub 7.02(3)}Ga{sub 1.98(3)}Sb{sub 6} and Eu{sub 7.04(3)}Ga{sub 1.90(3)}Sb{sub 6}-have been synthesized from reactions of the corresponding elements using gallium as a metal flux. Their crystal structures (space group I4-bar 3d (No. 220), Z=2 with unit cell parameters: a=9.9147(9) A for the Sr-compound; a=10.3190(9) A for the Ba-compound; and a=9.7866(8) A for the Eu-compound) have been established by single-crystal X-ray diffraction. The structures are best described as Ga-stabilized derivatives of the hypothetical Sr{sub 4}Sb{sub 3}, Ba{sub 4}Sb{sub 3} and Eu{sub 4}Sb{sub 3} phases with the cubic Th{sub 3}P{sub 4} type. Such an inclusion of interstitial Ga atoms in this atomic arrangement results in the formation of isolated [Ga{sub 2}Sb{sub 6}]{sup 14-} fragments, isoelectronic and isostructural with the [Sn{sub 2}Te{sub 6}]{sup 6-} anions in the K{sub 3}SnTe{sub 3} type, and allows for the attainment of a charge-balanced electron count. In that sense, the Sr{sub 4}Sb{sub 3}, Ba{sub 4}Sb{sub 3} and Eu{sub 4}Sb{sub 3} binaries, which are expected to be electron-deficient and are currently unknown, can be 'turned' into Sr{sub 7}Ga{sub 2}Sb{sub 6}, Ba{sub 7}Ga{sub 2}Sb{sub 6} and Eu{sub 7}Ga{sub 2}Sb{sub 6}, whose structures are readily rationalized following the Zintl concept. - Graphical abstract: Three new antimonides have been structurally characterized by single-crystal X-ray diffraction. Their structures are best described as derivatives of the body-centered cubic, anti-Th{sub 3}P{sub 4} type. Unlike the one-electron-deficient A{sub 4}Sb{sub 3} phases (A=Sr, Ba, Eu), the new, A{sub 7}Ga{sub 2}Sb{sub 6} compounds are Zintl phases with closed-shell configurations for both the cations and anions.
- OSTI ID:
- 21128391
- Journal Information:
- Journal of Solid State Chemistry, Vol. 181, Issue 8; Other Information: DOI: 10.1016/j.jssc.2008.04.004; PII: S0022-4596(08)00183-7; Copyright (c) 2008 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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