Effects of barium oxide on structure and properties of calcium iron phosphate glasses

• Studies were carried on glasses from xBaO-(20-x)CaO-32Fe2O3-48P2O5(x-2-18 mol%).
• Glasses with 4,8,12,16 mol% BaO were heated to generate crystals.
• Introduction of BaO would make glass network less compact.
• BaO would also improve the densities and thermal stability.
• BaO enhanced chemical stability of both alkali-resistance and acid-resistance.

In order to study the effects of barium oxide on the structure and properties of glasses from the glass system of xBaO-(20-x)CaO-32Fe2O3-48P2O5 (x = 2,4,6,8,10,12,14,16,18 mol%), several methods are applied to the investigation, including XRD, FTIR, DSC and chemical durability tests. Results from FTIR spectra shows that BaO loosens the glass network, with some sorts of crystals forming in the two glass groups depicted in the XRD spectra. However, the glass transition temperature (Tg) and glass crystalline temperature (Tc), as well as the difference between the two(ΔT = Tc-Tg), rise with the addition of BaO. All densities of glasses level up with larger concentration of barium oxide; fluctuations occur in the glass system with the formation of different crystals. When CaO is replaced by BaO, the dissolution rate moves to high level in alkali solution when compared with the basic glass (20CaO-32Fe2O3-48P2O5), while glasses in acid solution possess the inferior resistance than glasses in alkaline solution. It turns out that crystals in these glasses did improve resistance to acid and alkaline ions when they are compared with their base glasses.