Synthesis and spectroscopic characterization of strontium magnesium silicate phosphors for white afterglow applications

Abstract

Eu 2+ and Dy 3+ ion–activated strontium magnesium silicate phosphors were prepared using a modified solid-state method and two silicon sources: silicon oxide and silicon nitride. Dy 3+ ions were deliberately used to form various trap levels in the host band structure and thus achieve long-lasting performance of the silicate host. The coexistence of Sr 2 MgSi 2 O 7 and Sr 3 MgSi 2 O 8 phases was observed in the X-ray diffraction patterns obtained for phosphors synthesized from various silicon oxide to silicon nitride molar ratios. Photoluminescence spectra contained two broad bands at 464 nm (blue) and 540 nm (yellow) for the same host owing to 4f 7 –4f 6 5d transitions of Eu 2+ ions. The phosphors prepared using higher percentages of silicon nitride exhibited white light emission with chromaticity of (0.28, 0.32). A persistent white afterglow decay time of 10 s was determined using time-resolved spectroscopy for the phosphors prepared using high percentages of silicon nitride. A low-temperature thermoluminescence peak with a trap depth of 0.49 eV and lifetime of 140 s was found to be responsible for the afterglow properties of the strontium magnesium silicate phosphors. The present study demonstrated the suitability of using the obtained silicate phosphors for near-white-afterglow applications.