SUPERCONDUCTING METASTABLE PHASE IN RAPID QUENCHED Y-PD-B-C BOROCARBIDES

Rapid quenched (RQ) palladium-based borocarbides with large fractions of the superconducting phase (T-c>20 K) have been obtained. Supercondu ctivity is found to exist only in the RQ state. Thus, while the as cas t YPd2B2C is nonsuperconducting, the RQ material superconducts acid ha s an x-ray diffraction (XRD)-pattern characteristic of a face-centered cubic fee lattice with a lattice parameter of 4.15 Angstrom. A sequen tial annealing study shows decay of the superconducting phase above 75 0 degrees C which correlates well with the reduction in the integral i ntensities of the XRD fee peaks. A tentative phase diagram for superco nductivity in the Y-Pd-B-C systems is presented. (C) 1996 American Ins titute of Physics.