Syntheses, crystal and band structures, and magnetic and optical properties of new CsLnCdTe₃ (Ln = La, Pr, Nd, Sm, Gd-Tm, and Lu)

A series of new quaternary semiconductor materials CsLnCdTe₃ (Ln = La, Pr, Nd, Sm, Gd-Tm, and Lu) was obtained from high-temperature solid-state reactions by the reactive halide flux method. These compounds belong to the layered KZrCuS₃ structure type and crystallize in the orthorhombic space group Cmcm (No. 63). Their structure features two-dimensional ∞²[LnCdTe₃^-] layers of edge- and vertex-sharing LnTe₆ octahedra with Cd atoms filling the tetrahedral interstices, which stack along b-axis. The Cs atoms are located between the ∞²[LnCdTe₃^-] layers and are surrounded by eight Te atoms to form a CsTe₈ bicapped trigonal prism. Such Te layers are more flexible than the Se analogues in the isostructural CsLnMSe ₃ to accommodate nearly the entire Ln series. Theoretical studies performed on CsTmCdTe₃ show that the material is a direct band gap semiconductor and agrees with the result from a single-crystal optical absorption measurement. Magnetic susceptibility measurements show that the CsLnCdTe₃ (Ln = Pr, Nd, Gd, Dy, Tm) materials exhibit temperature-dependent paramagnetism and obey the Curie-Weiss law, whereas CsSmCdTe₃ does not.