CHARACTERIZATION OF 3 NEW TERNARY PHASES, NB(PD,AL)2 AND NB(RU,AL)2 OF TYPE MGZN2 AND NBRU2AL OF TYPE BIF3, IN THE SYSTEMS NB-PD-AL AND NB-RU-AL

The phase diagrams of both Nb-Pd-Al and Nb-Ru-Al were investigated in order to elaborate new niobium base alloys, with two-phase structures A2-B2 or A2-L2(1). Three new aluminides were identified. The first, Nb Ru2Al, was studied using single-crystal X-ray diffraction data; NbRU2A l is a Heusler phase alloy with space group Fm3mBAR and Z=4, a=6.135(1 ) angstrom, D(x)=9.27 g cm-3, mu(Mo Kalpha)=172.4 cm-1, F(000)=568, R= 0.033 (Rw=0.034) for 37 contributing unique reflections. The other pha ses, with formula Nb2(T(x)Al1-x)4 where T=Pd, Ru and 0.17(Pd) (0.19(Ru ))<x<0.26(Pd) (0.29(Ru)), were characterized by the Laves phase MgZn2- type structure.