Hydrothermal synthesis and structure of Li₄B₄Si₈O₂₄

The new composition Li₄B₄Si₈O₂₄ has been synthesized as single crystals employing a hydrothermal recrystallization technique and studied using single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2₁ with Z = 2 and cell parameters a = 5.0448(2), b = 13.1688(4), c = 13.3933(2) Å, β = 90.069(2)°. The structure is composed of (201) layers of corner connected B- and Si-centered tetrahedra forming four-, five- and six-membered rings. These units are then joined via Si-O-Si linkages to form a unique 3-D framework structure. The lithium atoms can be considered as forming part of a lithoborosilicate framework or to be well ordered within the pores formed by the borosilicate structure. (C) 2000 Elsevier Science Ltd.