We have investigated the homogeneity of sol‐gel derived YBa2Cu307‐s from thesolution phase to the final product using transmission electron microscopy(TEM), x‐ray diffraction (XRD), and Energy Dispersive X‐ray (EDX) lateralmapping techniques. The starting solutions contain stoichiometric amounts ofthe metal 2‐(2‐methoxyethoxy)ethoxide components in2‐(2‐methoxyethoxy)ethanol and appear to be homogeneous by TEM with auniform distribution of particles having an average size of less than 40 â.Through elemental mapping we see elemental segregation in the hightemperature (950 °C) products, which are orthorhombic by XRD. In elementalmaps of gel samples fired to 700 °C, which are tetragonal by XRD, we alsosee elemental inhomogeneity within particles and phase zoning in maps ofproducts from finely ground gels. A comparison of elemental maps and x‐raydiffraction patterns of the products from gel processing and conventionalsolid state processing is made.

Homogeneous solutions of yttrium, barium and copper 2-(2-methoxy)-ethoxyethoxides in 2-(2-methoxy)ethoxyethanol of appropriate lY:2Ba:3Cu stoichiometry have been prepared and used in sol-gel synthesis of YBa2Cu3O7-δ. To our knowledge, this is the first report of the preparation of a homogeneous solution of yttrium, barium and copper homoleptic alkoxides dissolved only in the parent alcohol. These solutions provide an excellent starting point for sol-gel synthesis of YBa2Cu3O7-° since the metals are mixed on the molecular scale, and because the solutions are stable with no possibility of ligand exchange to give insoluble products. Hydrolysis and careful heat treatment of gels produced from these solutions yield nearly pure tetragonal YBa2Cu3O7-δ at temperatures as low as 725°C. The preparation of these solutions and their characterization by small-angle x-ray scattering measurements and TEM are reported, as well as preliminary data pertaining to their use in the sol-gel synthesis of YBa2Cu3O7-δ.