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Borocarbide and silicocarbide intermetallic Y2NixB82xC2 ~x51, 2, 3, 5!, YNiCuB2C, and YNixCu22xSi2C ~x50, 2! were prepared and their superconductivity was studied. The results indicated that with the change of the ratio of Ni to B in Y2NixB82xC2 , secondary phases were introduced into YNi2B2C phase. A Tc of 15.0 K was observed for the compounds x52, 3, and 5, which originated from the major phase YNi2B2C in these samples. Partial substitution of Ni by Cu reduced the Tc to 11.0 K for YNiCuB2C. For Si substitution system, no bulk superconductivity was found in YNi2Si2C and YCu2Si2C. But a minor superconducting phase ~Tc;4 K! with a volume fraction of the order of near 1% was observed in them. It was noticed that for the temperature dependent magnetization of superconducting compounds containing Ni, a significant difference between zero-field cooling and field cooling curves before Tc was always observed, which was tentatively attributed to Ni-containing impurity. © 1996 American Institute of Physics.



Copyright 1996 AIP (American Institute of Physics) Publishing LLC.