Superconducting YBCO ceramics after exposure to a plasma flow to a mixture of argon and oxygen

The structure and properties of superconducting nanostructured ceramics YBa ₂Cu ₃O_7-y (YBCO) before and after exposure to a plasma flow consisting of a mixture of argon and oxygen (at ∼ 600 °C for ∼ 1 min) are investigated. Plasma surface treatment, in addition to compaction of grains, leads to a change in the oxygen stoichiometry index and average crystallite size, as well as to a decrease in the proportion of the superconducting phase in the ceramic. After plasma treatment of ceramics, the character of the temperature dependence of the electrical resistance ρ = f (T) changes from metallic to semiconductor, and the temperature T _{c, onset} remains constant. (paper)