A Single Crystal Study of RE14Co3In3 (RE = Y, Tb, Dy, Ho, Er)

Abstract

The rare earth-cobalt-indides RE14Co3In3 (RE = Y, Tb, Dy, Ho, Er) were prepared in polycrystalline form from the elements by arc-melting. Small single crystals were grown through a special annealing sequence. The compounds were investigated on the basis of X-ray powder and single crystal data: Lu14Co2In3 (Gd14Co3In2.7) type, P42/nmc, Z = 4, a = 959.0(1), c = 2319.1(5) pm, wR2 = 0.055, 2289 F2 values, 65 variables for Y13.90Co2.99In3.02, a = 953.8(1), c = 2315.8(5) pm, wR2 = 0.108, 2357 F2 values, 65 variables for Tb13.92Co3.01In2.92, a = 949.24(3), c=2296.5(1) pm, wR2= 0.129, 2518 F2 values, 65 variables for Dy13.90Co2.97In2.95, a=946.3(1), c = 2289.0(5) pm, wR2 = 0.099, 2297 F2 values, 64 variables for Ho14Co2.80In2.89, and a = 941.0(1), c = 2274.2(5) pm, wR2 = 0.140, 2450 F2 values, 65 variables for Er13.83Co2.88In3.10. All RE14Co3In3 indides show a small degree of In/Co mixing (between 7 and 16% Co) on the 4c In1 site and defects on the 8g Co1 positions (between 84 and 95% Co). Except for the holmium compound, the RE14Co3In3 intermetallics also reveal RE/In mixing on the 4c RE1 sites, leading to the refined compositions. The seven crystallographically independent RE sites have between 9 and 10 nearest RE neighbors. The RE14Co3In3 structures consist of a complex intergrowth of rare earth based polyhedra. Both cobalt sites have a distorted trigonal-prismatic rare earth coordination. An interesting feature is the In2-In2 dumb-bell with an In2-In2 distance of 300 pm (for Ho14Co2.80In2.89). The crystal chemistry of the RE14Co3In3 indides is discussed.