Chemical durability and physical properties of the Ho₂O₃·Al₂O₃·SiO₂ glass system

The glass formation region of the Ho2O3∙Al2O3∙SiO2 system was determined to extend from 9 to 30 mole percent Ho2O3. The chemical durability of these glasses was examined in physiological solutions to determine the feasibility of their use for in-vivo radiotherapeutic applications. The dissolution rates of bulk glass specimens were barely measurable in distilled water at 37 or 70 °C, but increased with temperature and with the substitution of Ho2O3 for Al2O3 or SiO2 in 0.1 N HCl. Both glass surface analysis by EDS and solution analysis by ICP showed that little if any holmium leached from bulk glass specimens or microspheres into the distilled water or saline solution at 37 or 70 °C. EDS and ICP also indicate that the predominant corrosion mechanism in 0.1N HCl is dependent on glass composition and temperature. The density, refractive index, thermal expansion, and Vickers hardness increased with Ho2O3 content. The structure of the glasses was examined by FTIR --Abstract, page iv