Effect of strontium and phosphorus source on the structure,morphology and luminescence of Sr5(PO4)2SiO4:Euphosphor prepared by solid-state reaction

Sr₅(PO₄)₂SiO₄:Eu²⁺ phosphosilicate phosphor was prepared by high temperature solid-state reaction. Effects of strontium sources (strontium oxide, strontium nitrate and strontium carbonate) and of phosphorus sources (diammonium phosphate, strontium monophosphate) on the reactivity of their mixture during heating and on phase composition, morphology and photoluminescence excitation and emission properties of the phosphors were investigated by TG–DTG–DSC, XRD, SEM and photoluminescence spectroscopy. The sequence of the solid-state reactions when using the different starting reagents was discussed based on the TG–DTG–DSC results. It was found that it is hard to prepare pure Sr₅(PO₄)₂SiO₄:Eu²⁺ phosphor with either of strontium sources studied when stoichiometric (NH₄)₂HPO₄ was used as a phosphorus source. Minor Sr₂SiO₄ impurity phase was present in the phosphors. The content of impurity phase, the morphology and resultant photoluminescence properties of the phosphors were markedly influenced by the strontium source employed. When SrCO₃ was used as the strontium source, the phase purity of the phosphor was improved with the addition of excess (NH₄)₂HPO₄. When (NH₄)₂HPO₄with 5% excess or SrHPO₄ in stoichiometric ratio was used as the phosphorus source a pure phase phosphor was obtained. In addition, the morphology and photoluminescence of the phosphor were also influenced by phosphorus source. The possible reasons causing different properties of the phosphors prepared using different raw materials were discussed based on reaction schemes.