Preparation and Jc of (Cu,Ag)Ba2Ca3Cu4Oy and CuxBa2Ca3Cu4Oy

Nearly single phase polycrystalline samples of (Cu,Ag)Ba2Ca3Cu4Oy and CuxBa2Ca3Cu4Oy have been synthesized by a high-pressure synthesis method. The samples were characterized by X-ray diffraction analysis and electrical resistivity measurements. The magnetic field dependence of intragrain Jc for as-sintered and proton irradiated samples was estimated from measurements of magnetic hysteresis using Bean critical state model. Improvement of Jc by proton irradiation was observed at low temperature below 40 K. The intragrain Jc at 5 K and 5 T was enhanced from 105 A/cm2 to 106 A/cm2.