Synthesis, crystal structures and spectroscopic properties of pure YSbOBr and YSbOCl as well as Eu- and Tb-doped samples

The quaternary halide-containing yttrium( iii ) oxidoantimonates( iii ) YSb 2 O 4 Cl and YSb 2 O 4 Br were synthesised through solid-state reactions from the binary components (Y 2 O 3 , Sb 2 O 3 and YX 3 , X = Cl and Br) at 750 °C in evacuated fused silica ampoules with eutectic mixtures of NaX and CsX (X = Cl and Br) as fluxing agents. YSb 2 O 4 Cl crystallizes tetragonally in the non-centrosymmetric space group P 42 1 2 with unit-cell parameters of a = 773.56(4) pm and c = 878.91(6) pm, whereas YSb 2 O 4 Br is monoclinic (space group: P 2 1 / c ) with a = 896.54(6) pm, b = 780.23(5) pm, c = 779.61(5) pm and β = 91.398(3)°, both for Z = 4. The two new YSb 2 O 4 X compounds contain [YO 8 ] 13 polyhedra, which are connected via four common edges to form layers ( d (Y 3+ -O 2− ) = 225-254 pm) without any Y 3+ X − bonds ( d (Y 3+ X − ) > 400 pm). Moreover, all oxygen atoms belong to ψ 1 -tetrahedral [SbO 3 ] 3− units, which are either connected to four-membered rings [Sb 4 O 8 ] 4− in the chloride (Y 2 [Sb 4 O 8 ]Cl 2 for Z = 2) or endless chains in the bromide (Y 1/2 (SbO 2 )Br 1/2 for Z = 8) by common vertices. With distances of 307 pm in YSb 2 O 4 Cl and 326 pm in YSb 2 O 4 Br there are not even substantial bonding Sb 3+ X − (X = Cl and Br) interactions at work. Luminescence spectroscopy on samples doped with trivalent europium and terbium showed an energy transfer from the oxidoantimonate( iii ) moieties as the sensitizer in the host structure onto the lanthanoid activators. The oxygen atoms of the two new compounds belong to ψ 1 -tetrahedral [SbO 3 ] 3− units, which are either vertex-connected to four-membered rings in YSb 2 O 4 Cl or to endless chains in YSb 2 O 4 Br. Eu 3+ - and Tb 3+ -doped samples show red or green luminescence.