SrBi2OB4O9 is a novel centrosymmetric borate oxide forming in the SrO–Bi2O3–B2O3 system. Its crystal structure has been determined ab initio from high-resolution X-ray and neutron powder diffraction data with the help of 11B MAS-NMR data. SrBi2OB4O9 crystallizes with a triclinic unit-cell with a=6.8657(1) Å, b=9.7976(1) Å, c=6.8148(1) Å, α=109.1270(8)°, β=101.8971(8)°, γ=96.1445(8)°, V=416.17(1) Å3, Z=2, space group P-1. Its structure consists of Bi2O4+ layers alternating along the b axis with SrB4O94− layers containing isolated B4O96− (〈2Δ〉Δ) tetraborate anions.
