Morocco exports phosphates and is exploring new applications for local phosphate mining resources, we have turned our attention to phosphate materials derived from the xNaI-(0.5-x)Li2O-0.125WO3-0.375P2O5 with (x=0, 0.1, 0.2, 0.25, 0.3, 0.4, 0,5). Phosphate glasses are less durable than silicate glasses; lithium replaces sodium, causing structural changes. This study focuses on the electrical conductivity of oxide glasses in the xNaI-(0.5-x)Li2O-0.125WO3-0.375P2O5, and in particular the effect of incorporating two modifiers or the effect of mixed alkalis. The results are noted as:(i)the mixed-alkali glasses (Li/Na) exhibit slower dissolution and higher chemical durability than single-alkali glasses, with the strongest durability enhancement around Na/(Na+Li) ≈ 0.5–0.6; (ii)The mixed-alkali effect (MAE) reduces alkali ion mobility, which suppresses proton exchange and slows dissolution; larger alkali ions contribute most to the MAE; (iii) Dissolution and conductivity are non-additive: glasses with only Li or Na are more conductive (Li > Na) and have lower activation energies, while MAE introduces a pronounced minimum in conductivity at certain compositions (near Na/(Na+Li) ≈ 0.6) and can raise the activation energy there; (iiii) In phosphate glasses, introducing alkalis lowers melting temperature but increases water sensitivity; MAE arises from redistribution/mobility changes of Li and Na ions within the phosphate network.
Abbas et al. (Fri,) studied this question.