Sol-gel preparation and properties of TiO2-P2O5 bulk glasses

Monolithic transparent and colorless, or Ti3+-free TiO2-P2O5 glasses containing very large amounts of TiO2 (up to 93 mol%) were successfully prepared by heat-treating the xerogels, which were made from titanium tetra-isopropoxide and triethyl phosphate, through the sol-gel reaction. The density and refractive index n(632.8 nm) of the sol-gel-derived glasses were higher than the melt-derived glasses of the corresponding compositions. The glasses of TiO2 content of larger than 80 mol% seemed somewhat porous, but n(632.8) of these glasses was very high as 2.2-2.3. Higher density and higher n(632.8 nm) than the melt-derived glasses were considered to be due to more abundance of six-fold coordinated Ti4+ ions. (C) 2004 Elsevier Ltd. All rights reserved.