China: Jiaozuo Companion — precipitated silica

Abstract

A non-aqueous wet-chemical method has been developed for the haloperovskite, K3GaF6. The powder X-ray diffractogram of the sample was fitted by Rietveld refinement with a lattice constant, a = 8.5285 (10) Å (space group Fm3¯m). Ga-F stretching mode was observed at 497 cm−1 in the FTIR spectrum. In the 19F NMR spectrum, signals at 153 and 180 ppm confirmed the presence of GaF6 octahedral units in the structure. The ligand-to-metal charge transfer (LMCT) transition appeared at 290 nm in the UV–vis absorbance spectrum generated by converting the reflectance data using Kubelka-Munk function. Following this success, K3GaF6 samples doped with 3 mol% of Eu3+, Er3+, Tb3+ and Er3+(2 mol%); Yb3+ (1 mol% co-doped) were prepared. Intra configurational f-f transitions in the UV–vis absorption spectrum were evident only for Er3+doped samples. Normal emissions (Stokes emission) in red, green regions arising from Eu3+, Tb3+ and Er3+ were observed in their photoluminescence spectra. Upconverted emissions of Er3+ and Er3+:Yb3+in the green and red regions were observed on exciting doped samples with laser of λ = 980 nm as confirmed from the corresponding CIE plots. The number of photons involved in the upconversion process was determined along with the estimation of decay time for the emission from Er3+:Yb3+ co-doped sample. A composite of Er3+;Yb3+ co-doped sample with optically transparent polymer, PMMA was fabricated and it exhibited uniform green glow after illuminating it with 980 nm laser.