Synthesis, crystal structures and luminescence properties of the Eu3+-doped yttrium oxotellurates(IV) Y2Te4O11 and Y2Te5O13

Y2Te4O11:Eu3+ and Y2Te5O13:Eu3+ single crystals in sub-millimeter scale were synthesized from the binary oxides (Y2O3, Eu2O3 and TeO2) using CsCl as fluxing agent. Crystallographic structures of the undoped yttrium oxotellurates(IV) Y2Te4O11 and Y2Te5O13 have been determined and refined from single-crystal X-ray diffraction data. In Y2Te4O11, a layered structure is present where the reticulated sheets consisting of edge-sharing [YO8]13− polyhedra are interconnected by the oxotellurate(IV) units, whereas in Y2Te5O13 only double chains of condensed yttrium–oxygen polyhedra with coordination numbers of 7 and 8 are left, now linked in two crystallographic directions by the oxotellurate(IV) entities. The Eu3+ luminescence spectra and the decay time from different energy levels of the doped compounds were investigated and all detected emission levels were identified. Luminescence properties of the Eu3+ cations have been interpreted in consideration of the now accessible detailed crystallographic data of the yttrium compounds, providing the possibility to examine the influence of the local symmetry of the oxygen coordination spheres.