Probing the limits of the Zintl concept: Structure and bonding in rare-earth and alkaline-earth zinc-antimonides Yb9Zn 4+xSb9 and Ca9Zn4.5Sb9

Svilen Bobev, Joe D. Thompson, John L. Sarrao, Marilyn M. Olmstead, Håkon Hope, Susan M. Kauzlarich

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Abstract

A new transition metal Zintl phase, Yb9Zn4+xb 9, was prepared by high-temperature flux syntheses as large single crystals, or by direct fusion of the corresponding elements in polycrystalline form. Its crystal structure was determined by single-crystal X-ray diffraction. Its Ca-counterpart, hitherto known as Ca9Zn4Sb 9, and the presence of nonstoichiometry in it were also studied. Yb9Zn4+xb9 was found to exist in a narrow homogeneity range, as suggested from the crystallographic data at 90(3) K (orthorhombic, space group Pbam (No. 55), Z = 2): (1) a = 21.677(2) Å, b = 12.3223(10) Å, c = 4.5259(4) Å, R1 = 3.09%, wR2 = 7.18% for Yb 9Zn4.23(2)Sb9; (2) a = 21.706(2) Å, b = 12.3381(13) Å, c = 4.5297(5) Å, R1 = 2.98%, wR2 = 5.63% for Yb 9Zn4.380(12)Sb9; and (3) a = 21.700(2) Å, b = 12.3400(9) Å, c = 4.5339(4) Å, R1 = 2.75%, wR2 = 5.65% for Yb9Zn4.384(14)Sb9. The isostructural Ca 9Zn4.478(8)Sb9 has unit cell parameters a = 21.830(2) Å, b = 12.4476(9) Å, and c = 4.5414(3) Å (R1 = 3.33%, wR2 = 5.83%). The structure type in which these compounds crystallize is related to the Ca9Mn4Bi9 type, and can be considered an interstitially stabilized variant. Formal electron count suggests that the Yb or Ca cations are in the +2 oxidation state. This is supported by the virtually temperature-independent magnetization for Yb9Zn 4.5Sb9. Electrical resistivity data show that Yb 9Zn4.5Sb9 and Ca9Zn 4.5Sb9 are poor metals with room-temperature resistivity of 10.2 and 19.6 mΩ·cm, respectively.

Original languageEnglish (US)
Pages (from-to)5044-5052
Number of pages9
JournalInorganic Chemistry
Volume43
Issue number16
DOIs
StatePublished - Aug 9 2004

ASJC Scopus subject areas

  • Inorganic Chemistry

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