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Title: Treparation of lithium niobate nanocrystals and nanocomposites
Author: Harun, Ahmad Mukifza
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2013
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The rapid advancement in electronic industries is driven by variety in electronic and electrical miniaturization concept design. Enhancement in performance, for example better scaling, stable response, less performance fatigue and miniaturization is at the heart or global research interest. Consistent with this concept, this research targets the development of a ferroelectric composite comprising inorganic ferroelectric and ferroelectric polymer, with potential for applications as the gate in ferroelectric fielq effect transistors. The inorganic ferroelectric material in this research was lithium niobate. Lithium niobate is known to have a high Curie temperature and low permittivity value. Even though lithium niobate (LiNbO3) possesses very good ferroelectric properties there are relatively few instances in which these properties are exploited in terms of composites. nus first research stage was to investigate the preparation of LiNb03 nanocrystals for use in a thin film nanocomposite. This stage describes the preparation and characterization of LiNbO3 nanoparticles. LiNbO3 has been prepared successfully via a molten salt route at 6500c using lithium chloride and lithium carbonate as a flux and niobium oxide as niobium source. This resulted in a very high crystallinity with nanocrystals on average 90 - 120 nm in diameter. The study also analyzed the optimum degree of crystallinity in the ferroelectric polymers, PVDF and P(VDF-TrFE). In order to achieve high crystallinity in PVDF and its copolymer, the spin coated polymer substrate needs to be annealed to a certain temperature. The optimum temperature to ensure the , highest crystallinity is found to be in the range 1300c - 140"C. Vacuum annealing also increased the crystallinity to a certain degree. The properties of a composite mixture between polymer P(VDF-TrFE) and LiNb03 were studied to understand its ferroelectric characteristics. The composite, with 0-3 connectivity, was processed using 3 different types of surface active agents; silane, poly (acrylic acid co-maleic acid) and a commercial deflocculant, KD!. A microstructure study showed only sUane provided strong binding between the matrix and LiNbQ3 particles. Polarization - electric field (P-E) hysteresis loops proved to be unsaturated; however a calculation showed that only 40% of the applied voltage was applied to the LiNbO3 particles, because of difference in permittivity values of each constituent hence the coercive field was not exceeded. The composite permittivity was also graphically fitted to a theoretical formula (Lichtenecker and Yamada) to understand its microstructure pattern connectivity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available