HIGH PRESSURE SYNTHESIS OF La 4 Au METASTABLE SUPERCONDUCTING PHASE

In this puper, we report the synthesis of a new metastable phase La 4 Au by means of high pressure high temperature treatment of an amorphous alloy. As starting material, the La 80 Au 20 amorphous ribbons were prepared from melt by rapid quenching method. Synthesis conditions were found to be at about 80kbar and 250℃. This new phase has a orthorhombic structure with lattice parameters a = 6.54?, b = 7.71? and c=11.32?, and exhibits superconducting transition at T c =5.5 K which is higher than that of any known La-Au phases.