Syntheses, structures, and physical properties of LnAsTe (Ln = La, Pr, Sm, Gd, Dy, Er)

Six rare-earth arsenic tellurides have been synthesized by the reactions of the rare-earth elements (Ln) with As and Te at 1123 K. LaAsTe (a = 7.8354(11) Å, b = 4.1721(6) Å, c = 10.2985(14) Å, T = 153 K), PrAsTe (a = 7.728(2) Å, b = 4.1200(11) Å, c = 10.137(3) Å, T = 153 K), SmAsTe (a = 7.6180(16) Å, b = 4.0821(9) Å, c = 9.991(2) Å, T = 153 K), GdAsTe (a = 7.5611(15) Å, b = 4.0510(8) Å, c = 9.920(2) Å, T = 153 K), DyAsTe (a = 7.4951(13) Å, b = 4.0246(7) Å, c = 9.8288(17) Å, T = 153 K), and ErAsTe (a = 7.4478(1) Å, b = 4.0078(1) Å, c = 9.7552(2) Å, T = 153 K) crystallize with four formula units in the orthorhombic space group D(2h)¹⁶-Pnma. These compounds are isostructural and belong to the β-ZrSb₂ structure type. In each compound, the Ln atoms are coordinated by a tricapped trigonal prism of four As atoms and five Te atoms. The entire three-dimensional structure is built up by the motif of the LnAs₄Te₅ tricapped trigonal prisms. Infinite nonalternating zigzag As chains are found along the b axis, with As-As distances in these compounds ranging from 2.5915(5) to 2.6350(9) Å. Conductivity measurements in the direction of these As chains indicate that PrAsTe is metallic whereas SmAsTe and DyAsTe are weakly metallic. Antiferromagnetic transitions occur in SmAsTe and DyAsTe at 3 and 9 K, respectively. DyAsTe above 9 K follows the Curie-Weiss law.