EXAFS spectroscopic study of PbO-Bi2O3-Ga2O3 glasses

Extended X-ray absorption fine structure (EXAFS) spectra for ternary heavy metal oxide glasses with compositions of (1 - x)(0.75PbO + 0.25Ga(2)O(3)) xBi(2)O(3) where x increased from 0 to 0.4 in 0.1 increments, indicate the formation of GaO4 tetrahedral unit with Ga-O bond length of similar to 1.8 7 A in all glasses. Pb also forms both PbO3 and PbO4 polyhedra, but the ave rage oxygen coordination number around lead decreases from 3.50 to 2.96 wit h decreasing PbO concentration. From the EXAFS data we conclude that Bi for ms BiO5 and BiO6 units as it does in the alpha-Bi2O3 crystal. Two distinct Bi-O distances of similar to 2.18 and similar to 2.46 A were resolved. Form ation of each type of the polyhedra results in shortage of total oxygen ion s for forming two-fold coordinated oxygens and as a result, formation of th ree-coordinated oxygens becomes necessary. (C) 1999 Elsevier Science B.V. A ll rights reserved.