Effects of silver additions on the mechanical properties and resistance tothermal shock of YBa2Cu3O7-delta superconductors

We evaluated the effects of silver (Ag) additions on the mechanical propert ies and resistance to thermal shock of bulk YBa2Cu3O7-delta (YBCO) supercon ductors. Various amount of Ag was added to YBCO by two different mixing tec hniques, i.e. in the form of metallic Ag powder and AgNO3 powder. It was ob served that the bending strength (strength), fracture toughness and resista nce to thermal shock of YBCO increased with increasing Ag content, probably due to strengthening mechanisms by the addition of Ag. In addition, YBCO-A g composites made by mixing with AgNO3 showed slightly higher strength, fra cture toughness and resistance to thermal shock as compared with those made by mixing with metallic Ag powder. The improvement in the resistance to th ermal shock is believed to be due to improvements in the strength, fracture toughness and thermal conductivity of YBCO-Ag composites resulting from Ag additions. (C) 1999 Elsevier Science Ltd. All rights reserved.