Microstructure and optical limiting properties of multicomponent inorganic gel-glasses: A focus on SiO2, TiO2 and PbO gel-glasses

Two kinds of multicomponent inorganic gel-glasses, namely, SiO₂–TiO₂ binary and SiO₂–TiO₂–PbO ternary gel-glasses, were obtained via the hydrolysis and co-condensation of tetraethyloxysilane (Si(OC₂H₅)₄, TEOS), titanium tetraisopropoxide (Ti(C₄H₉O)₄, TTIP), and lead (II) acetate trihydrate (Pb(Ac)₂). X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and pore structure measurements were performed to investigate the morphology, structure, and texture properties of the gel-glasses. The samples were mainly composed of amorphous phase without any detected phase separation. The introduced Ti⁴⁺ and Pb²⁺ were partially involved in the hydrolysis and condensation processes. Furthermore, the composition had a significant influence on the pore structure of silica-based gel-glasses, and the introduction of TiO₂ in the gel-glasses caused the formation of bimodal-distributed pore shapes and dimensions in multicomponent inorganic gel-glasses. The optical limiting (OL) properties were measured at 532 nm by using the open aperture Z-scan technique. The SiO₂–TiO₂ binary and SiO₂–TiO₂–PbO ternary gel-glasses exhibited greatly enhanced OL behaviors than the SiO₂ unitary gel-glass. The observed OL phenomenon in the SiO₂–TiO₂ binary gel-glass originated from two-photon absorption (TPA), whereas TPA followed by nonlinear scattering (NLS) contributed to the increased OL performance of the SiO₂–TiO₂–PbO ternary gel-glass. SiO₂–TiO₂ binary and SiO₂–TiO₂–PbO ternary gel-glasses are potential materials for practical applications in the fields of optics, all-optical switching, and related optical devices.