A new compound, dilithium aluminium pentaborate, Li2Al-B5O10, has been synt
hesized by solid-state reaction and its structure determined by single-crys
tal X-ray diffraction. This compound is composed of [B5O10](5-) groups link
ed by AlO4 tetrahedra. The [B5O10](5-) group consists of two hexagonal B-O
rings perpendicular to each other connected by tetracoordinated boron. All
the B-O rings in this structure can be divided into two groups, with one gr
oup approximately parallel and the other perpendicular to the c axis.