Sol–gel synthesis of monolithic tin-doped silica glass

The preparation of Sn-doped SiO ₂ glasses with different Sn contents (Sn/(SiO ₂ + SnO ₂ ) ratio 0.01 to 10.0% w/w) was performed by two sol–gel routes. The first route (method A) used tin(IV) tert-butoxide as the tin precursor and in the presence of acetylacetone it resulted in transparent glasses with a maximum tin content of 0.1%. The precursor in the second route (method B) was dibutyltin diacetate; this was more efficient and transparent glasses of up to 1% tin content were obtained. As electron paramagnetic resonance can identify paramagnetic E′ Sn centres, defects that form when silica glass is subjected to X-ray irradiation, we assessed the tin centres that substituted silicon in the silica network.At higher tin contents (Sn ≥ 3%), method B gave crystalline nanosized particles of SnO ₂ (6–10 nm) dispersed throughout the silica matrix.