The glass forming regions in the systems of Na2O-Fe2O3-(SiO2 or B2O3) and CaO-Fe2O3-(SiO2, B2O3 or GeO2) were determined.
(Na2O or CaO)-Fe2O3-SiO2 glasses were found to be capable of containing up to 30mole % Fe2O3, while (Na2O or CaO)-Fe2O3-(B2O3 or GeO2) glasses up to 20mole % Fe2O3. The glass forming region in the system (Na2O or CaO)-Fe2O3-(SiO2 or B2O3) was narrower than that in the system (Na2O or CaO)-Al2O3-(SiO2 or B2O3). Although the density of the CaO-Fe2O3-SiO2 glasses increased linearly with Fe2O3 content when CaO/SiO2 ratio was kept constant, the molar volume increased with Fe2O3 content. On the other hand at constant Fe2O3 content, the molar volume decreased with increasing CaO/SiO2 ratio. This implies that Fe2O3 tends to loosen the glass structure and CaO to tighten the glass structure in the systems containing less than 40mole % SiO2.
The dissolution ratio of Ca2+ ions in water was almost constant for all the glasses studied, while that of Fe3+ ions varied considerably. The dissolution ratio of Fe3+ ions decreased when SiO2 was replaced by CaO or Fe2O3, and it became 1/10 when Fe2O3 was partially replaced by CaO. Such changes were considered to be associated with the variation of the coordination number of Fe3+ ions in the glass. The electrical conductivity of the CaO-Fe2O3-SiO2 glasses changed from 10-6 to 10-11/ohm-cm, depending upon the Fe2O3 content. This variation may be explained by the change in interatomic distances of iron ions in the glass.
