Volume 49 (2006)

FT- IR AND AFM CHARACTERIZATION OF SOL-GEL DERIVED NANOCRYSTALLINE Zn₂SiO₄:Mn²⁺ PHOSPHORS
Pages 69-72
Corina Enache, Cecilia Savii, Eugenia Fagadar-Cosma, Daniela Dascalu, Claudia Ionescu

Abstract
Manganese activated willemite is an efficient green phosphor. Nanocrystalline powders of manganese doped willemite phosphors, ZnO·1.1SiO₂)·xMnO (0.21 L x L 0.85), have been obtained via sol-gel route. Beside tetraethoxysilane, water, ethanol, and different catalysts have been employed. In the reaction mixture different inorganic salt solutions, as zinc and manganese (II) sources have been added. The precursor xerogels were successively thermally treated up to 1000oC, for 180 minutes time soaking. During thermal treatment, the evolution of the system was monitored by using both Thermal Analysis and FT-IR spectroscopy. By using atomic force microscopy (AFM), high-resolution imaging has been obtained, permitting to directly observe the surface morphology. By taking into account the shifts of the Si-O stretching, IR specific features and of the Zn-O stretching vibrational modes, from 1096 cm-1 to 940 cm-1, and from 505 cm-1 and 455 cm-1 to 548 cm-1, respectively, the formation of Si-O-Zn linkage was put in evidence for the samples calcined at 700oC. Starting from 900oC thermally treated samples, the arising IR signals corresponding to willemite vibration modes have been observed. AFM pictures revealed an average particle diameter situated in nanometer range. Keywords: willemite, phosphors, sol-gel method.