Synthesis, crystal structures and spectroscopic properties of pure YSb2O4Br and YSb2O4Cl as well as Eu3+- and Tb3+-doped samples

The quaternary halide-containing yttrium(III) oxidoantimonates(III) YSb2O4Cl and YSb2O4Br were synthesised through solid-state reactions from the binary components (Y2O3, Sb2O3 and YX3, X = Cl and Br) at 750 degrees C in evacuated fused silica ampoules with eutectic mixtures of NaX and CsX (X = Cl and Br) as fluxing agents. YSb2O4Cl crystallizes tetragonally in the non-centrosymmetric space group P42(1)2 with unit-cell parameters of a = 773.56(4) pm and c = 878.91(6) pm, whereas YSb2O4Br is monoclinic (space group: P2(1)/c) with a = 896.54(6) pm, b = 780.23(5) pm, c = 779.61(5) pm and beta = 91.398(3)degrees, both for Z = 4. The two new YSb2O4Cl compounds contain [YO8](13-) polyhedra, which are connected via four common edges to form (2)(infinity){[YO(8/2)r(e)](5-)} layers (d(Y3+-O2-) = 225-254 pm) without any Y3+center dot center dot center dot X- bonds (d(Y3+center dot center dot center dot X-) > 400 pm). Moreover all oxygen atoms belong to psi(1)-tetrahedral [SbO3](3-) units, which are either connected to four-membered rings [Sb4O8](4-) in the chloride (Y-2[SB4O8]O-2 for Z = 2) or endless chains in the bromide (Y-1/2(SbO2)Br-1/2 for Z = 8) by common vertices. With distances of 307 pm in YSb2O4Cl and 326 pm in YSb2O4Br there are not even substantial bonding Sb3+center dot center dot center dot 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.