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Li-Containing Coloured Intermetallic Compounds and Chalcogenides
- Author / Creator
- Jomaa, Mohammed Yagoub Ahmed
This thesis describes the synthesis of Li-containing intermetallics and chalcogenides using high-temperature solid-state reactions and induction heating, with the aim of studying their structures, electronic properties, and optical properties to gain insights into their potential applications in jewellery and nonlinear optical devices.
The first part of this thesis focuses on coloured intermetallic compounds, which have a long history in decorative and jewellery applications, with gold and platinum-based alloys being among the very earliest examples. The objective was to identify new coloured substances based on non-precious and less expensive components. Several coloured Li-containing intermetallics were discovered, including purple Li2ZnGa, light blue Li2ZnIn, light blue LiMgCdGe. The colour can be controlled in the series of solid solutions LiCu2Al1–xGax and LiCu2–yNiyGa. All of these compounds adopt cubic structures in different space groups, as determined by powder X-ray diffraction. To clarify ambiguities about the site distribution, 7Li solid-state nuclear magnetic resonance spectroscopy was applied. The colours of these materials were quantified by extracting chromaticity coordinates from optical reflectance spectra. Electronic structure calculations indicate that these compounds are metallic. The observed colours are proposed to arise from interband transitions.
The second part of this thesis tests the hypothesis that incorporating a mixture of Li and Ag atoms into commercially available NLO materials, such as AgGaS2 and AgGaSe2, could result in solid solutions with a balanced set of properties. Complete substitution of Li atoms for Ag atoms was achieved in AgAlSe2, AgGaSe2, and AgInSe2, resulting in the solid solutions LixAg1–xAlSe2, LixAg1–xGaSe2, and LixAg1–xInSe2. The crystal structures of solid solutions were
determined by single-crystal X-ray diffraction and solid-state 7Li nuclear magnetic resonance spectroscopy. The Ga-containing solid solution retains a tetragonal CuFeS2-type structure (space group 𝐼4̅2𝑑) throughout the entire range of Li content, whereas the Al and In-containing solid solutions transform from this tetragonal structure to an orthorhombic -NaFeO2-type structure (space group Pna21) as Li content increases past x = 0.50. The optical band gaps can be tuned to desired values. The second harmonic generation responses were comparable to benchmark materials. All compounds melt congruently at accessible temperatures. Electronic structure calculations were carried out to quantify the bonding in these compounds.
- Graduation date
- Fall 2023
- Type of Item
- Doctor of Philosophy
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.