Phase relations and superconducting properties of the Y-Ni-B-C system

The influence of composition and high-temperature heat treatment on phase c ontent and superconducting properties of the YNi2B2C phase was investigated , Phase relations in those parts of the Y-Ni-B-C quaternary phase diagram, which are relevant for the YNi2B2C intermetallic phase formation, were reve aled by x-ray diffraction, optical and scanning electron microscopy, and hi gh-temperature differential thermoanalysis. A widespread interval of superc onducting transition temperatures T-C = 10.4-15.2 K and small transition wi dth <0.3 K were determined from samples of different nominal compositions a fter high-temperature annealing. The different intrinsic properties are asc ribed to composition variations of the YNi2B2C phase and related to structu re parameters, residual resistance ratios, and element concentrations deter mined by the electron probe microanalysis.