9417185 Stacy The long-term goal of the proposed research is to prepare new metal oxides at temperatures below 400 C by selective precipitation from ionic liquids. The general strategy is to dissolve the reactants in a molten salt, and precipitate the oxide product either by adjusting the acidity, by changing the electrochemical potential, by supersaturating the melt by melt decomposition, or by adding a precipitating agent. This scheme, which is an alternative to more typical reaction routes involving solid-state reactions at relatively high temperatures (above 800 C), offers two key advantages. First, low-temperature processing is desirable for many applications of oxides, especially for the formation of thin films for devices in which high- temperature processing would destroy other components. Second, new materials that are not stable at elevated temperatures can be prepared. Specifically, the proposed research is concerned with the use of molten alkali metal and alkaline-earth metal hydroxides and nitrates for the preparation of transition metal oxides with the metals in high formal oxidation states. The chemistry of these two melts will be explored in an effort to prepare: A) copper oxides; B) rhodium oxides; and C) early transition metal oxides. Interest in the copper and rhodium oxides stems from the possibility of discovering new phases, potentially ones that exhibit superconductivity. For the early transition metal oxides, lowtemperature synthetic routes will be designed to known phases that are electronic ceramics, and potentially useful as device components. %%% Metal oxides, including most ceramics and cuprate superconductors, generally are prepared by solid-state reactions of reactant mixtures (e.g., metal oxides, carbonates, oxalates, and/or nitrates). These mixtures can be obtained by a variety of methods, including repeated grinding, co-precipitation, or sputtering . Upon heating, reactions occur due to solid-state diffusion. However, beca use of high energies of activation, relatively high temperatures (typically above 800 C) and long reaction times are required to enhance homogeneity and ensure complete reaction. As an alternative to this synthetic scheme, the proposed research will explore low-temperature solution routes to metal oxides involving the use of molten alkali and alkaline-earth metal hydroxides and nitrates as solvents. The utilization of fluxes for synthesis has become a valuable technology, especially for the preparation of high-quality single crystals and epitaxial films. These are essential for many measurements of structure and physical properties, and are
