Polymer-assisted Sol Gel Research Articles

Optical and structural properties of Zn 2SiO 4:Mn 2+ green phosphor nanoparticles obtained by a polymer-assisted sol–gel method

A novel procedure for Zn 2 SiO 4 :Mn 2+ phosphor powder synthesis based on a combination of sol–gel and combustion methods is presented. The procedure utilizes Zn-nitrate, Mn-nitrate, tetraethylorthosilicate and polyethylene glycol to produce gel, which is then combusted in a microwave oven to form Zn 2 SiO 4 :Mn 2+ powder and further annealed to crystallize in desired structure. The material has been investigated by X-ray diffraction, scanning electron microscopy, infrared and photoluminescence spectroscopy. These investigations showed well-crystallized powder particles exhibiting intense green light emission.

Effect of poly(vinyl acetate) on structure and property of bismuth-doped strontium titanate thin films derived by sol–gel method

Bismuth-doped strontium titanate thin films with pure perovskite phase have been successfully deposited on Pt (1 1 1)/Ti/SiO 2/Si substrate by polymer-assisted sol–gel method. Poly(vinyl acetate) (PVAc) in precursor solution promoted the formation of perovskite phase during the heat treatment. SEM results revealed an increasing thickness from 40 to 80 nm every single layer and a porous structure with the addition of PVAc. The addition of polymer made the dielectric constant decrease from 140 to 40 and the tunability slightly increase compared with films without polymer in precursor.

Soft synthesis and vacuum ultraviolet spectra ofYAG:Ce3+ nanocrystals:reassignment of Ce3+ energy levels

Ce3+-doped YAG nanoparticles have been synthesized at relatively low temperaturesby the co-precipitation and polymer-assisted sol–gel methods and characterizedby Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction(XRD) and x-ray absorption near-edge structure (XANES) measurements.Calcination of the product was carried out at temperatures between 800 and1100 °C. Products calcined at the lower temperature contained a greater proportion ofCe4+,and this contributed in part to the lower intensity of the characteristic yellow photoluminescence.The synchrotron radiation excitation spectrum of this yellow emission band exhibits bands due toCe3+ absorption as well as the host band gap. The origin of a luminescence band at about 300 nm obtainedunder band-gap excitation is discussed. Previous assignments of the 5d electronic energies inYAG:Ce3+ are critically assessed, and in the light of the new energy level and transitionintensity calculations a revised assignment is put forward for the 5d energy levels.