Zintl and Intermetallic Phases Grown from Calcium/Lithium Flux
Metal flux synthes is a useful alternative method to high temperature solid state synthesis; it allows easy diffusion of reactants at lower temperatures, and presents favorable conditions for crystal growth. A mixed flux of calcium and lithium in a 1:1 ratio was explored in this work; this...
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Florida State University
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| Online Access: | http://purl.flvc.org/fsu/fd/FSU_migr_etd-9143 |
| Summary: | Metal flux synthes is a useful alternative method to high temperature solid state synthesis; it allows easy diffusion of reactants at lower temperatures, and presents favorable
conditions for crystal growth. A mixed flux of calcium and lithium in a 1:1 ratio was explored in this work; this mixture melts at 300°C and is an excellent solvent for main group elements
and CaH₂. Reactions of p-block elements in a 1:1 Ca/Li flux have produced several new intermetallic and Zintl phases. Electronegative elements from groups 14 and 15 are reduced to anions in
this flux, yielding charge-balanced products. More electropositive metals from group 13 are not fully reduced; the resulting products are complex intermetallics. The reactions of tin or lead
and carbon in Ca/Li flux produced the analogous phases Ca₁₁Tt₃C8 (Tt = Sn, Pb) in the monoclinic C21/c space group (a = 13.2117(8) Å, b =10.7029(7) Å, c = 14.2493(9) Å, β = 105.650(1)° for
the Sn analog). These compounds are carbide Zintl phases that includes the rare combination of C₃⁴ and C₂² units as well as Sn⁴ or Pb⁴ anions. Ca/Li flux reactions of CaH2 and arsenic have
produced the Zintl phases LiCa₃As₂H in orthorhombic Pnma (a = 11.4064(7), b = 4.2702(3), c = 11.8762(8) Å), and Ca13As6C0.46N1.155H6.045in tetragonal P4/mbm (a = 15.7493(15), c = 9.1062(9)
Å). The complex stoichiometry of the latter phase was caused by incorporation of light element contaminants and was studied by neutron diffraction, showing mixing of anionic sites to achieve
charge balance. Ca/Li flux reactions with group 13 metals have resulted in several new intermetallic phases. Reactions of indium and CaH₂ in the Ca/Li flux (with or without boron) formed
Ca₅₃In₁₃B₄₋ₓH₂₃(2.4 < x < 4.0) in cubic space group Im-3 (a = 16.3608(6) Å) which features metallic indium atoms and ionic hydride sites. The electronic properties of this "subhydride"
were confirmed by ¹H and ¹¹⁵In NMR spectroscopy. Attempts to replace boron with carbon yielded Ca₁₂InC₁₃₋ₓ, (Im-3, a = 9.6055(8)Å) which contains C34- units. A very similar phase, Ba12InC18H4
(Im-3,a = 11.1415(8) Å), was grown from the reaction of indium, carbon, and LiH in Ba/Li flux. This compound also includes C₃⁴ units. Preliminary Ca/Li flux reactions of aluminum with other
main group elements have produced several new phases: a hydride clathrate Ca₃₁Al₂H₂₅ in cubic Fd-3m (a=18.0835(15) Å), Ca24Al2(C1-xHx)N2H16 in tetragonal P42/nmc (a=15.9069(12) Å,
c=13.7323(10) Å, and Ca4Al2N5 in orthorhombic Pna2₁ (a = 11.2331(1) Å, b=9.0768(8) Å, c=6.0093(5) Å. === A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of
Philosophy. === Fall Semester, 2014. === September 25, 2014. === Acetylide, Allenylide, Boride, Carbide, Hydride === Includes bibliographical references. === Susan Latturner, Professor Directing Dissertation; Albert Stiegman, Committee Member; Igor Alabugin, Committee Member. |
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