Ternary rare-earth zinc arsenides REZn 1– xAs 2 ( RE=La–Nd, Sm)

Abstract

The ternary rare-earth zinc arsenides REZn 1− x As 2 ( RE=La–Nd, Sm) were prepared by reaction of the elements at 800 °C. Single-crystal and powder X-ray diffraction analysis revealed a defect SrZnBi 2-type average structure for the La member (Pearson symbol tI16, space group I4/ mmm, Z=4; a=4.0770(9) Å, c=20.533(5) Å), in contrast to defect HfCuSi 2-type average structures for the remaining RE members (Pearson symbol tP8, space group P4/ nmm, Z=2; a=4.0298(5)–3.9520(4) Å, c=10.222(1)–10.099(1) Å in the progression from Ce to Sm). The homogeneity range is not appreciable (estimated to be narrower than 0.6<1− x<0.7 in SmZn 1− x As 2) and the formula REZn 0.67As 2 likely represents the Zn-rich phase boundary. The Ce–Nd members are Curie–Weiss paramagnets. LaZn 0.67As 2 shows activated behavior in its electrical resistivity, whereas SmZn 0.67As 2 exhibits anomalies in its temperature dependence of the electrical resistivity.