Synthesis and characterization of europium and dysprosium-doped distrontium magnesium disilicate phosphors obtained by complexation method assisted by microwave

Full text: The phosphor Sr₂MgSi₂O₇ :Eu²⁺,Dy³⁺, as well as many silicates and aluminates doped with rare earths, have been widely studied because of their long persistent luminescence and emission near the highest sensitivity to the human eye. The syntheses of oxides by wet chemistry methods have shown great potential in the control of the properties of the final products, especially materials for application in photonics. In the quest for improvement of the characteristics and properties of Sr₂MgSi₂O₇ :Eu²⁺,Dy³⁺, a method of synthesis using a pair of complexing agents as EDTA-citrates was used. The synthesis proceeded further by thermal pre-treatment with subsequent calcination in a resistor furnace to 1200 °C for 5 h in H₂ or using a microwave heating in CO atmosphere. Thermogravimetry indicated complete elimination of volatile organic precursors and nitrate when the temperature reaches 1080 °C, corresponding to a weight loss of about 40 %. The X-ray powder diffraction patterns show the formation of the desired crystalline Sr₂ MgSi₂O₇ phase though with some Sr₃MgSi₂O₈ . The content of elemental carbon after calcination is lower in the doped matrix than in those without dopants. The materials calcined in a resistive furnace have higher amounts of residual carbon than those calcined in a microwave oven. In the emission spectra, the band attributed to the 4f⁷ → 4f⁶5d¹ transition of Eu²⁺ shifts to higher energy with increasing residual carbon content. (author)