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 CsLnCdTe(3) (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)(infinity)[LnCdTe(3)(-)] layers of edge- and vertex-sharing LnTe(6) octahedra with Cd atoms filling the tetrahedral interstices, which stack along b-axis, The Cs atoms are located between the (infinity)2[LnCdTe(3)(-)] 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 CsLnCdTe(3) (Ln = Pr, Nd, Gd, Dy, Tm) materials exhibit temperature-dependent paramagnetism and obey the Curie-Weiss law, whereas CsSmCdTe3 does not.