Synthesis and crystal structure of a new calcium borate, CaB6O10

A new calcium borate, CaB6O10, has been prepared by solid-state reactions at temperature below 750 °C. The single-crystal X-ray structural analysis showed that CaB6O10 crystallizes in the monoclinic space group P21/c with a = 9.799(1) Å, b = 8.705(1) Å, c = 9.067(1) Å, β = 116.65(1)°, Z = 4. It represents a new structure type in which two [B3O7]5− triborate groups are bridged by one oxygen atom to form a [B6O13]8− group that is further condensed into a 3D [B6O10]2−∞3 network, with the shorthand notation 6: ∞3[2 × (3:2Δ + T)]. The 3D [B6O10]2−∞3 network affords intersecting open channels running parallel to three crystallographically axis directions, where Ca2+ cations reside. The IR spectrum further confirms the presence of both BO3 and BO4 groups.