| Forty members of the ALnMQ3 (A = Rb, Cs; Ln = Rare-earth, Y; M = Mn, Zn, Cd, Hg; Q = S, Se, Te) family of semiconductors have been synthesized using the reactive-flux method at temperatures in excess of 1123 K. These isostructural materials crystallize in the layered KZrCuS3 structure type in the orthorhombic space group Cmcm. The structure is composed of two-dimensional 2infinity [LnMQ3] layers that stack perpendicular to [010] and are separated by layers of face- and edge-sharing AQ8 bicapped trigonal prisms. The materials are paramagnetic with the exception of CsYbZnS 3, RbYbZnSe3, and CsYbMSe3 (M = Mn, Zn) which exhibit a spin-glass-like transition near 10 K. The optical band gap energy of the ALnMQ3 compounds varies with chemical substitution from approximately 1.6 eV to 2.6 eV. Also, the optical band gap energy of the materials varies by up to 0.2 eV based upon crystal orientation. The calculation of the total and partial density-of-states of the CsYMSe3 (M = Zn, Cd, Hg) compounds indicate that the highest occupied molecular orbitals are primarily Se1 (4p) and Se2 (4p) in character, whereas the lowest unoccupied molecular orbitals have contributions from M (ns and np), Y (4d), and Se (4s and 4p). The colors and optical band gaps of the ALnMQ3 materials may be manipulated through a variety of chemical substitutions and that the compounds are an interesting and potentially useful new class of optical materials. |
