Effect of second-phase precipitates and deposition temperature on the hysteretic losses in CVD-prepared Nb3Ge

Hysteretic losses have been measured on a large number of Nb3Ge samples prepared by the chemical vapor deposition process. These measurements were performed as a function of induced current and temperature on samples which contained differing amounts of second-phase material, Nb5Ge3. It was found that very low 50-Hz losses, on the order of 20 μW/cm2 at 500 rms A/cm and at temperatures of up to 12 K, could be attained in as-deposited material. An apparent correlation between the critical current density and the Nb5Ge3 content was observed, which suggested that enhanced pinning due to the second-phase precipitates was responsible for these low losses.