Ternary rare-earth zinc arsenides REZn1–x As2 (RE=La–Nd, Sm)

Abstract: The ternary rare-earth zinc arsenides REZn1−x As2 (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 SrZnBi2-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 HfCuSi2-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 SmZn1−x As2) and the formula REZn0.67As2 likely represents the Zn-rich phase boundary. The Ce–Nd members are Curie–Weiss paramagnets. LaZn0.67As2 shows activated behavior in its electrical resistivity, whereas SmZn0.67As2 exhibits anomalies in its temperature dependence of the electrical resistivity. [Copyright &y& Elsevier]