The nature of the superconducting phase in yttrium palladium boride carbide

The superconducting multiphase material of nominal composition YPd₅B₃C_0.3 is investigated by means of light-optical metallography, high-resolution electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy. The phase morphology is found to depend sensitively on the conditions adopted during cooling from the melt. Superconductivity is linked to the occurrence of a needle-shaped phase. The structure of this phase is based on a body-centered tetragonal unit cell with a=0.375 nm and c=1.06 nm. It is concluded that the superconducting phase is based on a structure and stoichiometry equivalent to that of LuNi₂B₂C where Lu is replaced by Y and Ni by Pd.