Author(s)

Nadia Beloued¹, Zineb Chabbou¹, Said Aqdim^1,2*

¹Laboratoire de Génie des Matériaux pour Environnement et Valorisation, Faculté des Sciences, Université Hassan II Ain Chock, Casablanca, Morocco.
²Laboratoire de Chimie Minérale, Département de Chimie, Faculté des Sciences, Université Hassan II Ain Chock, Casablanca, Morocco.

Various characterisation techniques were used to study the composition of the glass series 55-P₂O₅-2Cr₂O₃-(43-x) Na₂O-xPbO (with 8 ≤ x ≤ 38; mole %) in terms of chemical durability, IR spectroscopy and scanning electron microscopy (SEM). The change in the dissolution rate as a function of time when the studied glasses were kept submerged in distilled water at 90°C for 20 days showed an improvement in the chemical durability when Na₂O content was substituted to PbO content. IR spectroscopy revealed a structural change from ultraphosphate groups to pyrophosphate, orthophosphate and probably ring metaphosphate groups. SEM revealed the existence of two phases: a vitreous phase and a crystalline phase. The presence of Cr₂O₃, even in small amounts, seems to play an important role in the formation of crystallites in the glass network. The improved chemical durability is attributed to the replacement of the easily hydrated Na-O-P and P-O-P bonds by covalent and resistant Pb-O-P bands. Both the increase in PbO content and in the Pb + Cr/P ratio causes an increase in the number of covalent Pb-O-P and Cr-O-P bonds, making the glass structure more rigid. The increase of the covalent Pb-O-P bands leads to a clear evolution of the structure and chemical resistance, caused by grain-boundary resistance as a result of glass crystallisation. The IR spectra indicate that the increase in PbO content favours the formation of isolated PO^3-₄ orthophosphate groups at the expense of pyrophosphate groups. The radical change in the structure from ultraphosphate groups to pyrophosphate and orthophosphate groups seems to be the cause of the formation of crystallites. The existence of crystallites in these glasses results in a marked improvement in their chemical durability. However, when the crystallites exceed a certain limit, the equilibrium between the glass bath and these crystallites is no longer maintained; we notice, once, a decrease in the chemical durability.

Phosphate Glasses, Chemical Durability, IR, SEM

Beloued, N. , Chabbou, Z. and Aqdim, S. (2016) Correlation between Chemical Durability Behaviour and Structural Approach of the Vitreous Part of the System 55P₂O₅-2Cr₂O₃-(43-x) Na₂O-xPbO. Advances in Materials Physics and Chemistry, 6, 149-156. doi: 10.4236/ampc.2016.66016.