Imaging of BaCuO2 impurity in solution-grown YBa2Cu3O7−δ

Abstract

Solid state reactions are the most commonly employed processes for the preparation of high-Tc superconducting ceramic oxides. However, there has been considerable effort expended to prepare the YBa2Cu3O7−δ (1-2-3) superconductor by low-temperature methods in order to obtain a more homogeneous oxide mixture resulting in products with superior superconducting properties. In our investigations, TEM was used to characterize the microstructure of these materials as a function of various processing parameters.The precursors for the (1-2-3) superconductors were prepared by precipitating hydroxides of Y, Ba, and Cu and heating the precipitates at various temperatures in the 750-930°C range for 12-60 hours in flowing O2. Crystals for electron microscopy were crushed, suspended in acetone, and dispersed onto holey carbon grids. TEM characterization was carried out on the Philips 400T operating at 120kV or on the JEOL 2000FX at the Texas Center for Superconductivity at the University of Houston.In this work, one of the impurity phases was observed and identified as BaCuO2.