Solid-state Syntheses, Crystal Chemistry and Optical Properties of Two Europium Oxide/sulfide Silicates,Eu2O(SiO4) and Eu5S(SiO4)3

摘要

Two europium oxide/sulfide silicates,Eu2O(SiO4) (1) and Eu5S(SiO4)3 (2),have been synthesized using high-temperature solid-state reactions.1 crystallizes in the monoclinic space group P21/C with a =9.1459(7),b =7.1280(5),c =6.7655(5) () and β=107.611(2)°,belonging to the Gd2O(SiO4) structure type;2 crystallizes in space group P63/m of the hexagonal system with a =9.786(4) and c =6.789(3) (),belonging to the apatite Ca5Cl(PO4)3 structure type.The structure chemistry of related RE2O(SiO4) and REsS(SiO4)3 compounds is also discussed.The optical energy gap of 2 is determined to be 2.05 eV.