Journal of the American Ceramic Society, Vol.92, No.6, 1250-1255, 2009
Ti3+-Free Titanoborophosphate Glasses as Molding Glasses with High Refractive Indices
Ti3+-free titanoborophosphate TiO2-B2O3-P2O5 (TBP)-based glasses were produced in order to obtain glasses with low T-g (<600 degrees C), high n(d) (> 1.8), and a short postannealing (PA) time (less than a few days). In addition, TBP- based glasses with low T-g (<570 degrees C), high n(d) (> 1.85), and a short PA time were successfully developed with the substitution of Li2O and ZnO for B2O3. Some glasses had very suitable properties for precision glass molding (T-g = 553 degrees C, n(d) = 1.851, PA time = 4 days for 6Li(2)O center dot 6ZnO center dot 55TiO(2)center dot 6B(2)O(3)center dot 27P(2)O(5) glass; T-g = 563 degrees C, n(d) = 1.880, PA time = 2 days for 5Li(2)O center dot 60TiO(2)center dot 10B(2)O(3)center dot 25P(2)O(5) glass; T-g = 566 degrees C, n(d) = 1.885, PA time = 3 days for 2.5Li(2)O center dot 2.5ZnO center dot 60TiO(2)center dot 10B(2)O(3)center dot 25P(2)O(5) glass; and T-g = 567 degrees C, n(d) = 1.890, PA time = 1 day for 5Li(2)O center dot 5ZnO center dot 60TiO(2)center dot 5B(2)O(3)center dot 25P(2)O(5) glass). The lambda(70%) of TBP-based glasses with n(d)>1.85 and commercially available molding glasses with n(d)>1.85 are 40-41 and 44-50, respectively, which means that these new glasses have even higher transparency in the visible region than those currently on the market. Thus, TBP-based glasses are considered to be promising materials as molding glasses with high transparency, low T-g, and high n(d).