Structural peculiarity and chemical durability of some lead-aluminum phosphate glasses

Abstract

In this study five series of glasses belonging to the general formula xAl2O3 ∙ (1 - x - y)PbO ∙ yP2O5 were prepared. In each of these series y was unchanged and the amount of alumina that could be added yielding a clear glass was found to depend on its value. The structure and aqueous resistance of the prepared glasses were investigated. The initial substitutions of AI2O3 for PbO considerably improve aqueous resistance of the glasses studied, whereas the subsequent substitutions have a much lesser effect. In turn, the influence of the initial substitutions on the aqueous resistance of the glasses is gradually diminished as the PbO contents of the base glasses (i.e., Al2O3-free glasses) are increased. Structurally, the dominance level of the Al(PO)4 moities was found to rise as the limiting composition was approached in each of the studied series. Moreover, the capability of these moieties to enhance glass crystallization was verified. In addition, PbO was found to enhance the formation of Q1-end groups in the glass structures. Glasses deviated from the uniform dissolution mechanism typical of phosphate glasses are classified into two subgroups according to the molar percentage value of the P2O5 component in their leached solution, as determined by the ICP measurements. The structural origins for these deviations were discussed.