PREPARATION AND PHASE-ANALYSIS OF YNI2B2C

The recently discovered superconducting compound YNi2B2C has been inve stigated regarding formation and phase composition for different start ing stoichiometries. The are-melted and annealed samples were examined by X-ray diffraction, scanning electron microscopy with EDX/WDX for l ocal compositional analysis, and differential thermal analysis. As-mel ted samples contain secondary phases which are reduced under appropria te annealing conditions. For a carbon-rich starting stoichiometry, pha se pure bulk YNi2B2C can be produced. In addition, the melting tempera ture of YNi2B2C has been determined by a pyrometric measurement. Since the first single crystals have been successfully grown with the aid o f a Ni-rich flux, Ni-rich starting stoichiometries were more closely i nvestigated for their phase composition.