Synthesis and characterization of zirconium-antimony binary and interstitial ternary intermetallic compounds

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1987
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Garcia, Eduardo
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Chemistry

The Department of Chemistry seeks to provide students with a foundation in the fundamentals and application of chemical theories and processes of the lab. Thus prepared they me pursue careers as teachers, industry supervisors, or research chemists in a variety of domains (governmental, academic, etc).

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The Department of Chemistry was founded in 1880.

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Abstract

A family of Zr[subscript]5Sb[subscript]3Z compounds, Z = C, O, Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, have been synthesized in the Mn[subscript]5Si[subscript]3 structure. The Z element occupies the center of confacial trigonal antiprisms of zirconium atoms. Antimony can also occupy the interstitial site, and the binary compound has a homogeneity range Zr[subscript]5Sb[subscript]3.0 to Zr[subscript]5Sb[subscript]3.4.;The compounds were mainly prepared by arc-melting or powder sintering. Temperatures in excess of 1100° C were needed to provide adequate reaction rates for the sintering experiments. Isothermal vapor transport reactions, 1100 < T <1300° C, with iodine as a transporting agent were used to ensure complete reaction, but provided no single crystals. Reactions using Zn or In as a solvent yielded single crystals of a size suitable for physical property measurements. Structural refinements were carried out for the compounds Zr[subscript]5Sb[subscript]3Al, Zr[subscript]5Sb[subscript]3Si, Zr[subscript]5Sb[subscript]3S, Zr[subscript]5Sb[subscript]3Fe, Zr[subscript]5Sb[subscript]3(Fe[subscript]2/3In[subscript]1/3).;Extended-Huckel band calculations were carried out on Zr[subscript]5Sb[subscript]3, Zr[subscript]5Sb[subscript]3S, and Zr[subscript]5Sb[subscript]3Fe in order to rationalize the ability of Zr[subscript]5Sb[subscript]3 to interstitially incorporate this remarkable array of chemically diverse elements. A high density of states at the Fermi energy, low lying and strongly bonding ZrSb states in the Zr[subscript]5Sb[subscript]3 host, and the strong bonding interactions between zirconium and the interstitial element, combine to permit the extensive interstitial chemistry observed;The zirconium-antimony binary system was reinvestigated in the course of the Zr[subscript]5Sb[subscript]3Z study. Five new phases were identified: Zr[subscript]5Sb[subscript]3 ( Y[subscript]5Bi[subscript]3-type), ZrSb[subscript]1-x (FeSi-type), ZrSb (ZrSb-type), ZrSb[subscript]2 ( PbCl[subscript]2-type), and Zr[subscript]2Sb[subscript]3. The structure type of an additional compound was elucidated, Zr[subscript]2Sb ( La[subscript]2Sb-type). The unique structure type for ZrSb was determined by a single crystal X-ray diffraction experiment, and structural refinements were also carried out for Zr[subscript]5Sb[subscript]3 ( Y[subscript]5Bi[subscript]3 and Mn[subscript]5Si[subscript]3) and ZrSb[subscript]2 ( PbCl[subscript]2).;Extended-Huckel band calculations were carried out on the two ZrSb[subscript]2 structural polymorphs, PbCl[subscript]2 and ZrSb[subscript]2 types. The results indicate a slight increase in Sb-Sb bonding and a decrease in Sb-Zr bonding in the ZrSb[subscript]2 structure compared with those in the PbCl[subscript]2 modification. The results also imply that there is only a limited amount of charge transfer in these compounds, and a Zintl phase description is inappropriate. ftn * DOE Report IS-T-1298. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.

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Thu Jan 01 00:00:00 UTC 1987