Synthesis, crystal structure, and optical properties of a new lead barium borate, PbBa2(B3O6)2

A new lead barium borate, PbBa2(B3O6)2, has been synthesized by the standard solid-state reaction at temperature in the range 700-750 °C. The crystal structure has been determined by single crystal X-ray diffraction. PbBa2(B3O6)2 crystallizes in the rhombohedral space group R3¯ with unit cell a = 7.2056(8) Å, c = 18.752(6) Å, and Z = 3. The nearly planar B3O6 groups serve as the fundamental building units, which are distributed layer upon layer perpendicular to the c axis. Regular PbO6 octahedra and irregular BaO9 polyhedra alternately locate between the B3O6 layers. DSC curve and the powder X-ray diffraction pattern of melted PbBa2(B3O6)2 illustrate that PbBa2(B3O6)2 melts incongruently. The IR spectrum further proves the presence of BO3 groups. The calculated band structures of PbBa2(B3O6)2 and the density of states have also been investigated.