The role of ionic liquids/deep eutectic solvents in sol-gel syntheses of complex metal oxides

  • Omar Gomez Rojas

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


In this work we discuss the mechanism of action of this technique and demonstrate its efficacy as a means to synthesise single-phase strontium niobates of controlled stoichiometry. Also, the interaction between an ionic liquid, 1-ethyl-3-methylimidazolium acetate (emim)OAc, and biopolymers. It was demonstrated how they are intimately involved in the control of shape, size and crystallinity of a strontium niobate, and the direct involvement of the oxygen content of the resultant crystal composition in the synthesis of YBa2Cu3O7−δ (YBCO) superconductor. 
An extensive mechanistic study of the synthesis of the high temperature superconductor YBa2Cu3O7−δ using different ionic liquids and deep eutectic solvents, as well as mono-molecular chelating agents is also presented. Key experimental factors required for the synthesis of a metal oxide were recognised, focussing on the identification of precursory phases and elements that will augment or disrupt the synthesis, thereby assuring finer control over the desired crystal composition. 
Furthermore, it is presented for the first time the use of a deep eutectic solvent (DES), namely betaine:D-(+)-glucose which is capable of solubilize insoluble-in-water metal salts, like barium nitrate, and produce after calcination, high yields (>90 %) of Bi2Sr2CaCu2O8+x (BSCCO or Bi-2212) superconductor. Moreover, the stability of the DES is studied along several days to comprehend how the evolution of the DES is directly involved in the synthesis of the metal oxide. Lastly, the synthesis of a new sodium strontium niobate crystal composition is reported, Na0.1Sr0.9NbO3, via a choline chloride-based DES by forming, during the calcination process, high temperature-stable crystal compositions which, eventually will re-combine to form and entirely new crystal composition. Additionally, as a comparative analysis the synthesis is also studied via (emim)OAc.
Date of Award23 Jan 2019
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorSimon R Hall (Supervisor) & Chris Bell (Supervisor)

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