Phase equilibria in the system Y-Ni-B-C

The phase content of powder metallurgically prepared samples has been investigated by means of chemical analysis, electron microprobe analysis, optical microscopy, differential thermal analysis and X-ray diffraction studies. At 1300 C the superconducting phase YNi2B2C is in equilibrium with several well known phases as well as with YNiB4-zCz. The latter is a new compound, which crystallizes isotypic to YCrB4. The other equilibrium phases are the liquid phase (from which YNi4B and Ni6.6B2.7C0.6 crystallize, the latter with the structure of Ni2B), YB2C2, YNiC2 and YNiBC. Investigations of the homogeneity range of YNi2B2C revealed boron deficiencies in dependence of the composition of the sample. Additionally, YNi2B2C turned out to be thermodynamically stable up to 1500 C. (orig.)