Materials Chemistry and Physics, Vol.163, 501-506, 2015
Crystal structure and Raman spectrum of Ba2Pb(B3O6)(2)
Ba2Pb(B3O6)(2) Polycrystalline powder was synthesized by a solid state reaction using BaCO3, Pb3O4 and H3BO3 as initial reactants. The crystal structure was solved from the powder X-ray diffraction data by the Rietveld refinement method and the DFT (density functional theory) calculation. The results show that Ba2Pb(B3O6)(2) is isostructural with the high-temperature phase BaB2O4 (Ba2Ba(B3O6)(2))(-) It crystallizes in the trigonal space group R (3) over bar c with a = b = 7.20295(3) angstrom, c = 37.594(1) angstrom, and Z = 6. The structure is built up of the layers of B3O6 rings that are separated by Ba2+ or Pb2+ cations. The Raman spectrum of Ba2Pb(B3O6)(2) was interpreted on the basis of the analysis through site group method. Its irreducible representation of the normal modes is 10A/g + 11A2g + 10A75 + 11A(2u) + 21E(g) + 21E(u) among which 10A(1g) + 11A(2g) + 10A(1u) + 10A(2u) + 21E(g) + 20E(u) are optical modes, where the A(g) and E-g are Raman active. The DFT calculated results confirmed the results of the site group analysis and assigned all peaks in the experimental Raman spectrum. The alpha-BaB2O4 Raman spectrum was recorded and compared with the Ba2Pb(B3O6)(2) Raman spectrum. The effect of the Pb2+ cations on the Raman intensity was discussed. (C) 2015 Elsevier B.V. All rights reserved.