Superconducting properties and microstructure of YBCO HTSC materials with K₂CO₃ addition

The influence of K₂CO₃ additive on the superconducting properties and microstructure of samples with nominal compositions Y_1-0.2xBa_2-0.2xK_xCu₃O_7-y, Y₁Ba₂Cu_3.5-xK_xCu₃O_7-y, (x=0 to 1.50). were investigated. Only traces of K (1×10^-1wt.%) were observed in all samples after the final baking and no proof could be found for alkali metal cations participating in the Perovskite crystal cell. Potassium carbonate eliminated the CuO second phase from the system, because of a KCu-compound formation which evaporated above 900° C. The influence of the K₂CO₃ was positive for x = 0.40 to 0.75 where we observed homogeneous grain-size ceramic structure and HTSC Y₁Ba₂Cu₃O_y sample with values of T_c = 93.4 K and ΔT = 1.5 k.