Preparation of YBa2Cu3O y crystals by electrolysis of YO1.5-BaO-CuO x melts

Mass transfer during the electrolysis of melts of Y_0.02Ba_0.30Cu_0.70O _y and Y_0.02Ba_0.25Cu_0.75O _y samples was studied at 950°C (for 0.5 h) and currents of 5–1050 mA. YBa₂Cu₃O_{6 + δ} (123) tetragonal oxide crystal boules were grown, and their cationic composition and structure were studied by X-ray powder diffraction and by electron diffraction and elemental analysis in a transmission electron microscope (ED/TEM and EA/TEM). The 123 oxide was found to have cationic off-stoichiometry and to have a domain structure with domain sizes of 20–50 Å. Magnetic susceptibility versus temperature curves measured in the crystals after oxygen annealing (450°C, 1 h) feature four kinks, which indicate the occurrence of four superconducting phases with T _c = 45, 52, 75, and 86 K. Electrolysis byproducts are platinum-containing oxides Ba₉Pt₄Cu₃O _y and Ba₅₀Pt₁₅Y₁₆Al₁₃Cu₇O _y unknown hitherto; we report structure data for them.