High-pressure preparation, crystal structure, and properties of the new rare-earth oxoborate β-Dy 2B 4O 9

Abstract

In this work we report about a new rare-earth oxoborate β-Dy 2B 4O 9 synthesized under high-pressure/high-temperature conditions from Dy 2O 3 and boron oxide B 2O 3 in a B 2O 3/Na 2O 2 flux with a walker-type multianvil apparatus at 8 GPa and 1000°C. Single crystal X-ray structure determination of β-Dy 2B 4O 9 revealed: P 1 ̄ , a=616.2(1) pm, b=642.8(1) pm, c=748.5(1) pm, α=102.54(1)°, β=97.08(1)°, γ=102.45(1)°, Z=2, R1=0.0151, w R 2=0.0475 (all data). The compound exhibits a new structure type which is built up from bands of linked BO 3- (Δ) and tetrahedral BO 4-groups (□). The Dy 3+-cations are positioned in the voids between the bands. According to the conception of fundamental building blocks β-Dy 2B 4O 9 can be classified with the notation 2Δ6□:Δ〈3□〉=〈4□〉=〈3□〉Δ. Furthermore we report about temperature-resolved in situ powder diffraction measurements and IR-spectroscopic investigations on β-Dy 2B 4O 9.