A study of the effect of KClO3 addition on the AC susceptibility and microstructure of high-temperature (T-c(onset) at 105 K) YBCO ceramic superconductors

Bulk Y1Ba2Cu3Oy superconductors with KClO3 or K2CO3 additives were synthesi zed by a solid state reaction method. The influence of additives on the AC susceptibility, morphology and microstructure of samples with nominal compo sitions Y1Ba2-xKxCu3Oy, Y1Ba2Cu3.5-xKxOy, Y1-0.2xBa2-0.2xKxCu3Oy, (x = 0.2) were investigated. Experimental results showed a promoting effect of the a dditives on the formation of 123 phase in air atmosphere. Only traces of po tassium were observed in all samples after the final backing, but chlorine was remained in the material. The superconducting transition temperature fo r all KClO3-doped samples was found to be higher than that for K2CO3-doped and undoped Y1Ba2Cu3Oy (YBCO). KClO3-doped Y1Ba1.8K0.2Cu3Oy with T-c(onset) at 105 K was obtained. The comparison of characteristics for samples with various potassium compound in the initial batch demonstrated that each addi tive had a specific effect on chi(T), Delta T-c and microstructure of YBCO high-temperature superconductors (HTSC). The results were discussed in term s of different interaction in which KClO3 and K2CO3 participate up to 900 d egrees C. (C) 1998 Elsevier Science B.V, All rights reserved.