A Novel Synthetic Method of Sr2Si5N8:Eu2+ from SrSi2O2N2:Eu2+ by Carbo-Thermal Reduction and Nitridation

We demonstrated a novel synthetic route from Eu2+-doped oxy-nitride phosphors to prepare Eu2+-doped nitride phosphors. The Eu2+-doped Sr2Si5N8 phosphor was prepared by carbo-thermal reduction and nitridation from Eu2+-doped SrSi2O2N2 mixed with carbon. Eu2+-doped SrSi2O2N2 phosphor was prepared at 1350-1500 degrees C, and subsequently Eu2+-doped Sr2Si5N8 phosphor was synthesized at 1550-1700 degrees C. When over 4 wt% of carbon was added, the phase of SrSi2O2N2:Eu2+ changed to the one of Sr2Si5N8:Eu2+. The data of photoluminescent spectra and X-ray powder diffraction (XRD) patterns proved the phase transition. The product showed a red emission of 616 nm at the blue excitation of 450 nm. The shape of phosphor changed from a plate type to a rod one. We also prepared some red phosphors of SrSixOoNn:Eu2+ according to the different ratio of Si. Although the Si content was different from each other, there was no change in XRD patterns.