ARC-MELTING SYNTHESIS AND CRYSTAL-CHEMISTRY OF RT2B2(C) (R = RARE-EARTH, T = RH, CO) COMPOUNDS

The effects of carbon content and rare earth size on the phase stabili ty and crystal chemistry of RT2B2(C) (R=rare earth, T=Rh, Co) compound s have been investigated using are-melting synthesis and X-ray diffrac tion. It was found that, for the transition metal cobalt, GdCo2B2Cx co mpounds could be obtained for x ranging from 0.0 to 1.0. The c-axis of the compound increases significantly with increase in carbon content, while the a-axis decreases slightly. For the transition metal rhodium , however, RRh2B2 could not be obtained for the largest lanthanide, La , or the smallest, Er. With the addition of C to the ternary system, n ew RRh2B2C compounds have been obtained for R=Y, La to Er, except Eu. The stability of the RRh2,B-2,C phase decreases with decreasing lantha nide size, which can be explained from the rare earth dependence of th e crystallographic parameters of the compounds. (C) 1998 Elsevier Scie nce S.A.