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

A series of Yb 2+ and Dy 3+ doped SrSi 2 O 2 N 2 phosphors with enhanced crystallinity and photoluminescence properties have been successfully synthesized by two-step method using Sr 2 SiO 4 as precursor. It is clearly indicated from XRD results that Yb 2+ ions can substitute Sr sites in SrSi 2 O 2 N 2 crystal and exhibit pure phase and well-crystalline in comparison with the samples prepared by traditional solid-state reaction. The excessive amount of Si 3 N 4 in the reactants promoted the formation of pure SrSi 2 O 2 N 2 phosphors phase. SrSi 2 O 2 N2: Yb 2+ 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 SrSi 2 O 2 N 2 : 0.01 Yb 2+ phosphor synthesized by two-step method. Due to the concentration quenching, the luminescence intensity reaches the maximum when doping concentration of Yb 2+ ions is 1 mol%, which is identified as the electric dipole-electric dipole interaction . Notably, Yb 2+ and Dy 3+ co-doped SrSi 2 O 2 N 2 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.