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 b y single crystal and powder X-ray diffractometry. The phases with R = Pr, N d, 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 re place the previously reported RCo3Sn phases. The slightly anomalous depende nce of the lattice constants on the rare earth size can be ascribed to stre ngthening of the Co-Sn bonds. (C) 2000 Elsevier Science S.A. All rights res erved.