SEARCH FOR NEW SUPERCONDUCTORS IN THE Y-NI-B-C SYSTEM

We have searched for superconductivity in a wide variety of stoichiome tries in the Y-Ni-B-C system, using Y-x(NiB)C-y phase spread alloy thi n films and the magnetic held modulated microwave absorption technique . The superconducting critical temperature (T-c) varies with the stoic hiometry, showing the highest T-c for a Y/Ni ratio of 1/2, attributed to the YNi2B2C phase. We found no other superconducting phases with a T-c higher than 10 K. Furthermore, a search in YxNiB(C1-zNz)(y) and Yx NiBNy phase spread alloys showed no superconductivity. (C) 1997 Americ an Institute of Physics.