Crystal structure of R3Co8Sn4 compounds (R=Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Y)

The R3Co8Sn4 compounds (R=rare earth) have been synthesized and studied by single crystal and powder X-ray diffractometry. The phases with R=Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu and Y crystallize in the Lu3Co7.77Sn4 structure type, but with full occupancy of all atomic positions, giving 3:8:4 stoichiometry in all cases except the lutetium phase. The studied phase was not found in the systems with La, Ce and Sc. These compounds should replace the previously reported RCo3Sn phases. The slightly anomalous dependence of the lattice constants on the rare earth size can be ascribed to strengthening of the Co-Sn bonds. (orig.)