THE PEROVSKITE CARBIDES A(3)MC (A=SC, Y,LA-ND, SM, GD-LU - M=AL, GA, IN, TL, SN, PB)

Twentyfive new perovskite carbides have been obtained either by are-me lting cold-pressed pellets of the elemental components with subsequent annealing at 900 degrees C or by heating stoichiometric quantities of the elements in a high-frequency furnace. Also, thirtyseven compounds of this structure type are confirmed and their lattice constants are reported. The crystal structures of Sc(3)MC (M = Al, Ga, In, Tl) were refined from X-ray powder data, and in all cases only the octahedral v oids formed by scandium atoms were found to be fully occupied. The hyd rolysis of the carbides Sc3GaC, Y3SnC, Y3PbC and Ho3PbC with diluted h ydrochloric acid resulted in about 84 - 97 (wt-)% methane and 3 - 16 % saturated and unsaturated higher hydrocarbons. The cell volumes of th e ternary carbides A(3)MC and the corresponding binary Cu3Au type comp ounds A(3)M are compared and several inconsistencies are pointed out.