Two new members of the lanthanoid bismuth oxide oxidosilicates LnBiO[SiO4] with Ln=La and Gd

Abstract

The isostructural lanthanoid bismuth oxide oxidosilicates with the formula LnBiO[SiO4] (Ln=La and Gd) crystallize in the triclinic space group urn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0001 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 urn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0002 {[LnOurn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0003 Ourn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0004 ]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 urn:x-wiley:00442313:media:zaac202300126:zaac202300126-math-0005 {[OLnurn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0006 Biurn:x wiley:00442313:media:zaac202300126:zaac202300126-math-0007 ]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.