Flux synthesis, crystal structure, and luminescence properties of a new europium fluoride-silicate: K₅Eu₂FSi₄O ₁₃

The crystal structure and luminescence properties of flux-grown crystals of a new europium(III) fluoride-silicate, K₅Eu₂FSi ₄O₁₃, are reported. The structure consists of octahedral dimers of the composition [Eu₂O₁₀F], which are linked by unbranched tetrasilicate chains to form a 3-D framework with 5- and 6-ring channels parallel to the b axis where the K⁺ cations are located. The sharp peaks in the room-temperature emission spectrum are assigned. The number of lines in the region for the ⁵D₀ → ⁷F₀ transition and the relative intensities of the ⁵D₀ → ⁷F₁ and ⁵D₀ → ⁷F₂ transitions confirm the presence of two local Eu³⁺ environments and strongly distorted Eu³⁺-ligand surroundings. The room-temperature fluorescence decay curves are well fit by a single-exponential function yielding a lifetime value of about 2.0 ms. Crystal data: monoclinic, space group P2₁/m, a = 7.1850(2) Å, b = 5.7981(2) Å, c = 18.1675(6) Å, β = 92.248(2)°, and Z = 2.