Effects of alkaline-earth metal oxides on structure and properties of iron phosphate glasses

In order to figure out the effects of alkaline-earth metal oxides on structure and properties of iron phosphate glass, the glass system (100-x) (60P2O5-40Fe2O3)-x RO (RO = MgO, CaO, SrO, x = 5,10,15,20 mol%) was investigated. Structure and properties were studied by XRD, FTIR, DSC, while chemical durability tests were carried in acid and alkali solution under harsh conditions for 120 h. Results from XRD show that not all glasses are amorphous. There are several crystals emerging in the three series of glasses. Meanwhile, FTIR tests demonstrate that as more RO was doped, the glass network depolymerized,with phosphate chains turning shorter; vibrations of all bands indicate the formation of P-O-R bands. Densities of all samples would move up with more RO, glasses with SrO being higher than those doped with MgO and CaO. The glass transition temperature (Tg) of all glasses increases, while the glass crystalline temperature (Tc) of glasses containing MgO and CaO grows up as well. However, glasses with SrO slump dramatically, which deteriorates thermal stability in this system. As for the chemical stability, weight loss for all glasses falls eventually with time both for acid and alkali solutions. The residential materials after alkali corrosion have several crystals when removed to XRD tests. Meanwhile, almost all samples left more intact after acid corrosion when compared with those suffering from alkali corrosion, indicating the superior acid resistance to alkali for glasses.