Effect of the glass composition on the chemical durability of zinc-phosphate-based glasses in aqueous solutions

The chemical durability of glasses with the composition 40P(2)O(5)-55ZnO-1Ga(2)O(3)-4Ag(2)O and 41P(2)O(5)-51ZnO-8Ga(2)O(3) (mol%) was studied by measuring the rates of aqueous dissolution in neutral, acidic and alkaline aqueous solutions and discussed as a function of the glass composition. The change in the pH of the solutions as a function of the immersion time of the samples was used to study the dissolution mechanism. Using XRD and SEMJEDXA, we showed that the dissolution in deionized (DI) water and HCl consists of the leaching of the phosphate chains into the medium along with (i) the formation of a hydrated layer with the composition Zn2P2O7 center dot 3H(2)O and also of AgCl agglomerates when immersed in HCI and (ii) a leaching out of P, Ca and Ag when immersed for more than 180 min in DI water and for more than 60 min in HCI. The dissolution in NaOH-Na2CO3 consists of a net consumption of the OH- along with the formation of layers of Zn-3(PO4)(2)center dot(H2O)(4) and Zn(H2PO2)(2)center dot H2O with no apparent diffusion of P, Ga and Ag when immersed for as long as 240 min. Increasing the Ga2O3 concentration in zinc-phosphate glass at the expense of Ag2O lowers the dissolution rate when immersed in DI water, HCI and NaOH-Na2CO3 probably due to a reinforcement of the glass network.