A simple gel to crystal conversion route has been followed for the preparation of nanocrystalline SnO₂ at 80–100°C under refluxing conditions. Freshly prepared stannic hydroxide gel is allowed to crystallize under refluxing and stirring conditions for 4–6 h. Formation of nano crystallites of SnO2 is confirmed by X-ray diffraction (XRD) study. Transmission electron microscopic (TEM) investigations revealed that the average particle size is 30 nm for these powders.

A gel was formed when a mixture of TiOCl₂ and tartaric acid was heated on a water bath. Ultrafine powders of TiO₂ in the anatase phase were formed, when the gel was decomposed at 623 K and the mole ratio of tartaric acid to titanium was 2. The anatase phase was converted into rutile phase on annealing at higher temperatures, > 773 K. When initial ratio of titanium to tartaric acid was < 2, the decomposition of gel leads to the formation of mixed phases of rutile and anatase. However, pure rutile phase was not formed by the decomposition of gel for any ratio of tartaric acid and titanium. These powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and surface area measurements. The average particle size obtained for anatase phase was 3 nm whereas it was 30 nm for rutile phase. Raman scattering experiments were also performed to confirm both anatase and rutile phases.

A gel was formed when a aqueous solution of BaCl₂, NbF₅ and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 600°C yielded the nano crystallites of BaNb₂O₆, as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000°C) as reported for the formation of BaNb₂O₆. Transmission electron microscopic (TEM) investigations revealed that the average particle size is 50 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 1000. The ferroelectric hysteresis loop parameters of these samples were also studied.