The influence of K2CO3 additive on the superconducting properties and microstructure of samples with nominal compositions Y1-0.2xBa2-0.2xKxCu3O7-y, Y1Ba2Cu3.5-xKxCu3O7-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 Y1Ba2Cu3Oy sample with values of Tc = 93.4 K and ΔT = 1.5 k.
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