Cd2 and Co2 dumbbell formation in the yttrium-rich intermetallic compounds Y14Ni3Cd3 and Y6Co2Zn

Abstract

Abstract The yttrium-rich intermetallic compounds Y14Ni3Cd3 and Y6Co2Zn were obtained by direct reactions of the elements in sealed tantalum tubes in an induction furnace. Both samples were characterized by X-ray powder diffraction and the structures were refined from single-crystal X-ray diffraction data: Lu14Co3In3 type, P42/nmc, a = 960.06(5), c = 2314.9(1) pm, wR2 = 0.0669, 2034 F 2 values, 63 parameters for Y14Ni3.16(2)Cd2.84(2) and Ho6Co2Ga type, Immm, a = 943.08(7), b = 950.08(7), c = 997.64(7) pm, wR2 = 0.0476, 981 F 2 values, 34 parameters for Y6Co2Zn. One cadmium site shows a small degree of Cd/Ni mixing, leading to the composition Y14Ni3.16(2)Cd2.84(2). Although both compounds crystallize with significantly different structure types, they show very similar monomeric building units: (i) transition metal centered trigonal prisms of yttrium, (ii) empty Y6 octahedra and (iii) icosahedral coordination of the cadmium respectively zinc atoms. The condensation patterns of these building units are discussed and for Y14Ni3.16(2)Cd2.84(2), we elaborate a crystal chemical building principle along with the rare earth metal-rich phases RE 15Rh5Cd2 (La15Rh5Cd2 type), RE 23 T 7 X 4 (Pr23Ir7Mg4 type), RE 4 TX (Gd4RhMg type) and RE 10 TX 3/RE 9 TX 4 (ordered Co2Al5 versions). The structures of Y14Ni3Cd3 and Y6Co2Zn show dumbbell formation: 306 pm Cd–Cd in Y14Ni3Cd3 and 224 pm Co1–Co1 and 246 pm Co2–Co2 in Y6Co2Zn.