Two New Members of the Lanthanoid Bismuth Oxide Oxidosilicates LnBiO[SiO4] with Ln=La and Gd

Abstract

AbstractThe isostructural lanthanoid bismuth oxide oxidosilicates with the formula LnBiO[SiO4] (Ln=La and Gd) crystallize in the triclinic space group with the lattice parameters a=571.04(3) pm, b=681.13(4) pm, c=697.98(4) pm and α=105.805(2)°, β=110.456(2)°, γ=99.871(2)°, Vuc=0.23380(2) nm3 for Ln=La and a=554.12(3) pm, b=670.68(4) pm, c=689.57(4) pm and α=104.619(2)°, β=110.793(2)°, γ=99.560(2)°, Vuc=0.22237(2) nm3 for Ln=Gd with Z=2 for both. Colorless single crystals were serendipitously obtained from the reaction of bismuth sesquioxide, bismuth trifluoride and the lanthanoid sesquioxides at 850 °C in unprotected torch‐sealed silica ampoules as SiO2 source. Their crystal structure features Ln3+ cations surrounded by eight oxygen atoms as distorted square antiprisms [LnO8]13−, which are linked via edges with three further polyhedra of this kind to form layers {[LnO O ]7−} within the (010) plane. The oxygen environment of the Bi3+ cations has to be described as ψ1‐octahedral (square pyramids [BiO5]7−) with five oxide ligands and the stereochemically active lone pair. Two of them are edge‐linked to form ψ1‐bioctahedra [Bi2O8]10−. Four out of five oxygen atoms belong to discrete [SiO4]4− tetrahedra, which separate {[OLn Bi ]4+} chains of trans‐edge connected [OLn2Bi4]10+ tetrahedral, centered by the fifth oxygen atom propagating along [100] for charge compensation. Furthermore, the magnetic properties of GdBiO[SiO4] were investigated, showing Curie‐Weiss behavior without any magnetic ordering phenomena down to lowest temperatures.