Enhanced crystallinity and photoluminescence properties of Yb2+ doped SrSi2O2N2 phosphor for image storage applications

Abstract

A series of Yb2+ and Dy3+ doped SrSi2O2N2 phosphors with enhanced crystallinity and photoluminescence properties have been successfully synthesized by two-step method using Sr2SiO4 as precursor. It is clearly indicated from XRD results that Yb2+ ions can substitute Sr sites in SrSi2O2N2 crystal and exhibit pure phase and well-crystalline in comparison with the samples prepared by traditional solid-state reaction. The excessive amount of Si3N4 in the reactants promoted the formation of pure SrSi2O2N2 phosphors phase. SrSi2O2N2: Yb2+ phosphors show emission band at 583 nm and the broad excitation peaks located at 308 nm, 384 nm and 447 nm, covering the emission wavelength of NUV and blue chips. Compared with the sample prepared by traditional one-step solid-state reaction method, a dramatic enhancement of photoluminescence emission intensity (∼1.75 times) can be observed for SrSi2O2N2: 0.01 Yb2+ phosphor synthesized by two-step method. Due to the concentration quenching, the luminescence intensity reaches the maximum when doping concentration of Yb2+ ions is 1 mol%, which is identified as the electric dipole-electric dipole interaction. Notably, Yb2+ and Dy3+ co-doped SrSi2O2N2 phosphors with pure phase exhibit a unique thermal-stimulated luminescence property under NUV excitation, indicating the potential application in optical information storage. Furthermore, the mechanism of thermal-stimulated luminescence has been proposed.