Structural dimension modulation in a new oxysulfide system of Ae(2)Sb(2)O(2)S(3) (Ae = Ca and Ba)

Inspired by the abundant structural diversity and potential applications of Sb-based oxysulfides, two new compounds with the same stoichiometry, Ae(2)Sb(2)O(2)S(3) (Ae = Ca, Ba), were successfully synthesized via solid state reactions. Both crystallize in the C2/c space group (no. 15) of a monoclinic system, however, possess different structural dimensions induced by different sizes of template alkaline-earth ions. Ca2Sb2O2S3 is composed of one-dimensional anionic [Sb2O2S3](4-) chains isolated by Ca2+ ions, while Ba2Sb2O2S3 consists of zero-dimensional anionic [Sb2O2S3](4-) clusters separated by Ba2+ ions. Higher structural dimension endows the 1D Ca2Sb2O2S3 with a higher melting point (m.p. = 720 degrees C) and a narrower band gap (E-g = 2.36 eV), compared with the m.p. = 692 degrees C and E-g = 2.78 eV of Ba2Sb2O2S3. Both exhibit interesting photoluminescence properties with multiemission characteristics. DFT calculations reveal that the band edges of Ae(2)Sb(2)O(2)S(3) are mainly composed of Sb-S bond orbitals, while O 2p orbitals also contribute to the valence band maximum of Ba2Sb2O2S3.