YBCO-BiO Composite Superconductor for Granular-Type Josephson Microwave Detector

Abstract
We have developed a new YBCO-BiO composite superconductor for granular-type Josephson microwave detectors. This composite superconductor was prepared by doping YBa2Cu3O x with Bi2O3 and it was found that the normal state resistance increased with the amount of Bi2O3 doping up to 15 wt.%, without deterioration at the zero-resistance temperature. BaBiO3 was segregated at the interface of the YBCO particles during sintering at a temperature of about 940°C. This seemed to enhance the resistance of the grain boundary and improve the microwave detection responsivity. Practical responsivity (R Mv) of 180 V/W and noise equivalent power (NEP) of about 1.4×10-14 W/√Hz were obtained using a YBCO-BiO detector with 15 wt.% Bi2O3 doping.

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