STABILIZATION OF SUPERCONDUCTING LNPT2B2C BY PARTIAL SUBSTITUTION OF GOLD FOR PLATINUM

The quaternary intermetallic compounds LnPt2B2C (Ln = La, Pr and Y) we re recently shown to be superconducting at temperatures up to 10.5 K. Annealing conditions were not found, however, which yielded single-pha se material. Here it is reported that the partial substitution of Au f or Pt in LnPt2B2C yields essentially single-phase polycrystalline mate rial under annealing conditions readily accessible by conventional tec hniques. This is accomplished through arcmelting LnPt1.5Au0.6B2C, a co mposition slightly superstoichiometric in transition metal, and anneal ing at 1100-degrees-C in Ta foil: a small amount of melt phase formed in the anneal is wicked away from the sample leaving good-quality mate rial behind.