Open Access

Ralf J. C. Locke, Martina Mikuta, Florian Ledderboge, Frank C. Zimmer, Henning A. Höppe, Thomas Schleid

• Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network ∞3{[Y5F3]12+} and the remaining part consists of ψ1-tetrahedral [AsO3]3− units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y5Cl3[AsO3]4 crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9)pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)◦ for Z = 4. Condensation of [(Y1,2)O8] 13− polyhedra via four common edges each leads to fluorite-like ∞2{[(Y1,2)O 8/2e] 5−} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)3+ cations with their Cl− ligands on the one hand and the As3+ cations with their lone-pairs of electrons on the other, which also form within [AsO3] 3− anions lone-pair channels along [010].Y5F3[AsO3]4 crystallizes needle-shaped in the tetragonal space group P4/ncc with the lattice parameters a = 1143.80(8) pm, c = 1078.41(7) pm and c/a = 0.9428 for Z = 4. The yttrium-fluoride substructure linked via secondary contacts forms a three-dimensional network ∞3{[Y5F3]12+} and the remaining part consists of ψ1-tetrahedral [AsO3]3− units, which leave lone-pair channels along [001]. In contrast, platelet-shaped Y5Cl3[AsO3]4 crystals adopt the monoclinic space group C2/c with the lattice parameters a = 1860.56(9)pm, b = 536.27(3) pm, c = 1639.04(8) pm and β = 105.739(3)◦ for Z = 4. Condensation of [(Y1,2)O8] 13− polyhedra via four common edges each leads to fluorite-like ∞2{[(Y1,2)O 8/2e] 5−} layers spreading out parallel to the (100) plane. Their three-dimensional linkage occurs via the (Y3)3+ cations with their Cl− ligands on the one hand and the As3+ cations with their lone-pairs of electrons on the other, which also form within [AsO3] 3− anions lone-pair channels along [010]. Both colorless compounds can be obtained by solid-state reactions from corresponding mixtures of the binaries (Y2O3, As2O3 and YX3 with X = F and Cl) at elevated temperatures of 825 ◦C, most advantageously under halide-flux assistance (CsBr for Y5F3[AsO3]4 and ZnCl2 for Y5Cl3[AsO3]4). By replacing a few percent of YX3 with EuX3 or TbX3, Eu3+- or Tb3+-doped samples are accessible, which show red or green luminescence upon excitation with ultraviolet radiation.…