Synthesis, crystal structure and optical properties of a new lithium dilead pentaborate, LiPb2B5O10

• A new lithium dilead pentaborate, LiPb2B5O10, has been synthesized.
• LiPb2B5O10 is a congruent melting compound.
• The band gap calculation of LiPb2B5O10 revealed an indirect gap with 3.433 eV.

A novel lithium dilead pentaborate compound, LiPb2B5O10, is synthesized by the high temperature solution method for the first time. It crystallizes in the monoclinic space group P21/m with lattice constants a = 4.4023(10) Å, b = 14.037(3) Å, c = 6.8846(16) Å, β = 107.408(2)° and Z = 2. The structure consists of B5O10 units, LiO4 and PbO7 polyhedra. The B5O10 unit is composed of three BO3 triangles and two BO4 tetrahedra. The IR spectrum further confirms the presence of both BO3 and BO4 groups. The calculated band gap via ab initio methods is about 3.433 eV, which is consistent with the experimental result obtained from UV–vis–NIR diffuse reflectance spectrum.