New Ternary Rare-Earth Transition-Metal Antimonides RE3MSb5 (RE = La, Ce, Pr, Nd, Sm; M = Ti, Zr, Hf, Nb)

Investigations into ternary rare-earth transition- metal antimonide systems RExMySbz have been going on for at least two decades.These studies have been carried out variously to search for new magnetic materials,1-3 to test the validity of bonding models,4'5 and perhaps most importantly, to systematize an in- teresting structural chemistry that is not as well understood as that of the corresponding phosphides or arsenides.2-16Some of these antimonides have counterparts in phosphides or arsenides, such as REMSbz (M = Mn-Zn, Pd, Ag, Au)2-6 with the HfCuSi2 struc- ture, REM2S\)2 (M = Mn, Ni, Pd)1'7-10 with the CaBe2- Ge2 and ThCr2Si2 structures, and REMtSbu (M = Fe, Ru, Os)11-12 with the filled skutterudite LaFe4Pi2 struc- ture.Others, such as RE3M3Sb4 (M = Pt, Cu, Au)13- 15and REMSbs (M = Cr, V),16 are unique to antimonides so far.We report here the synthesis of a new series of ternary antimonides REsMSbs containing an early transition metal M = Ti, Zr, Hf, Nb.The title compounds were prepared by reactions of powders of the rare-earth metals (RE = La, Ce, Pr, Nd, Sm; all 99.9%), transition metals (M = Ti, 99.98%; Zr, 99.7%; Hf, 99.8%; Nb, 99.8%), and antimony (99.999%), all obtained from Cerac.Initial investigations were carried out in the La/Ti/Sb phase system by analyzing arc-melted samples with diverse starting compositions.In general, 0.25-g samples were prepared in a drybox in the form of pressed pellets, which were then melted in a Centorr 5TA tri-arc furnace under argon (gettered by melting a titanium pellet) at slightly greater than atmospheric pressure.The cooled buttons were flipped over and remelted.Since some vapourization occurs during the arc-melting, the weight loss is assumed to (1) Mulder, F.