Syntheses, Local Environments, and Structure-Property Relationships of Solid- State Vanadium Oxide-Fluorides

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<p> Vanadium oxide-fluorides can exhibit properties of piezoelectricity, second harmonic generation (SHG) activity, electrochemical activity, and other phenomena. The first two properties derive from the second-order and Jahn-Teller distortions, respectively, of d⁰ and d¹ vanadium; the electrochemistry derives from the reduction of V^V to V^IV,III,II. </p><p> An examination of the immediate environment of a vanadium cation facilitates an understanding of how a cation influences the structure of a compound and its resulting properties. In the inorganic hydrate CuVOF₄(H₂O)₇, the CuVOF₄(H₂O)₆ basic-building unit (BBU) has a &Lambda;-shape that compels polar packing in a structure that has SHG properties. The compound is a very rare example of a carbonless, SHG-active molecular crystal. Influences for its packing are reasoned with principles previously used within organic molecular crystallography. </p><p> The early transition metals (ETMs) of vanadium, niobium, and molybdenum within compounds of formulae K₁₀(M₂O_nF_11-n)X (M = V^V, Nb^V, n = 2, M = Mo^VI, n = 4; X = halide) show a related packing motif of &Lambda;-shaped BBUs in different structures. Owing to the absence or presence of &Lambda;-shaped BBUs, these heterotypical structures crystallize decidedly into SHG-inactive or SHG-active forms when M = V^V or M = Nb^V, Mo^VI, respectively. The future use and development of &Lambda;-shaped BBUs within solid-state systems can result in SHG-active materials. </p><p> The material CuVOF₄(H₂O)₇ presents an interesting coordination: the late transition metal (LTM, Cu^II) coordinates solely to the oxide anion of the vanadyl cation owing to hard-soft acid-base (HSAB) properties. The materials Na₂[M(H₂O)₂][V₂O₄F₆] (M^II = Co, Ni, Cu) show the LTM coordinates solely to the oxide anions of the V^V cation while the alkali cation (Na^I) coordinates solely to the fluoride anions. These HSAB properties were used to generate layers of hard or soft cation/anion rich regions in the electrochemically-active double wolframite AgNa(VO₂F₂)₂. </p><p> These structure-property examinations of solid state vanadium oxide-fluorides are presented as principles for (i) fundamental understanding of ETM and BBU crystallographic environments, (ii) materials discovery for fundamental investigations, (iii) materials design, and (iv) materials for use in SHG, piezoelectric, and electrochemical processes.</p>

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Identifer	oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3615500
Date	23 May 2014
Creators	Donakowski, Martin Daniel
Publisher	Northwestern University
Source Sets	ProQuest.com
Language	English
Detected Language	English
Type	thesis