Mechanical and superconducting properties of Ag/YBCO composite superconductors reinforced by the addition of Zr

The composite high T_Csuperconductor Ag/YBCO reinforced by adding Zr has been synthesized by sintering a compressed mixture of Zr_xYBa₂Cu₃O_7-δ(0≤x≤1.0) and Ag powders at various ratios. The flexural strength in the Ag/ZYBCO reached its maximum value of 280 MPa at the composition x=0.8 and 33 vol.%Ag, being more than 5 times as large as that in the sintered YBCO. In addition, the presence of Ag can endow the plasticity while maintaining the superconducting transition temperature above about 80 K. Both the flexural strength and the Vickers hardness are enhanced in magnitude comparable to those for commercial alumina and magnesia. The enhanced mechanical strength is attributed to the unique microstructure, in which dispersed Ag particles remain intact with the Zr-bearing YBCO matrix, whereas CuO and BaZrO₃precipitates in the 123-phase matrix act to reinforce the ceramic without disrupting the superconducting channel.