YBCO-BIO COMPOSITE SUPERCONDUCTOR FOR GRANULAR-TYPE JOSEPHSON MICROWAVE DETECTOR

We have developed a new YBCO-BiO composite superconductor for granular -type Josephson microwave detectors. This composite superconductor was prepared by doping YBa2Cu3Ox with Bi2O3 and it was found that the nor mal state resistance increased with the amount of Bi2O3 doping up to 1 5 wt.%, without deterioration at the zero-resistance temperature. BaBi O3 was segregated at the interface of the YBCO particles during sinter ing at a temperature of about 940-degrees-C. This seemed to enhance th e resistance of the grain boundary and improve the microwave detection responsivity. Practical responsivity (R(M)v) of 180 V/W and noise equ ivalent power (NEP) of about 1.4 X 10(-14) W/square-root Hz were obtai ned using a YBCO-BiO detector with 15 wt.% Bi2O3 doping.