THE MICROSTRUCTURE AND ELECTRICAL-PROPERTIES OF LOW-RESISTANCE CONTACTS TO YBA2CU3O7-DELTA CERAMICS

Contacts with resistivities of 10(-8) Ohm cm(2) or less, at temperatur es below the T-c of the underlying YBCO material, have been formed by incorporating gold wires into silver contact pads in a single heat tre atment. Voltage-current characteristics of these contacts show superco nducting behaviour. Microstructural cross-sections show an Ag/Au alloy with an Ag:Au atomic ratio of 3:1. Contacts made by applying wires af ter the silver heat treatment, which do not form an Ag/Au alloy, show residual resistances below T-c of around 0.5-50 m Ohm. Susceptibility and resistivity measurements were not suitable for critically differen tiating between contact methods or treatment temperatures.