Synthesis, structure and spectroscopic properties of Nd3+:SrY2O4 phosphor

Abstract

In order to obtain new-type laser crystals, SrY2O4 is chosen as a host material. Because Y3+ ions in SrY2O4 occupy two non-equivalent sites, it might be possible to realize dual-wave laser and broadband emission at 1.06 m by partially replacing Y3+ with Nd3+. In this work, (3 at.%) Nd3+ doped SrY2O4 phosphor is synthesized by the conventional solid state reaction. The structure and luminescence properties in the visible and near-infrared ranges are studied. The peaks in the X-ray powder diffraction pattern of (3 at.%) Nd3+:SrY2O4 can be well indexed according to ICSD#25701. The lattice parameters, atomic coordinates, atomic temperature factors etc., are obtained by the Rietveld refinement with R_p of 4.68% and R_wp of 5.91%. According to the excitation spectra in a range of 220-380 nm, it can be seen that Nd3+:SrY2O4 is efficiently excited by 353 nm which is assigned to the 4I9/24D3/2+4D5/2+2I11/2+4D1/2 transition of Nd3+ ions. Under the 353 nm light excitation, Nd3+:SrY2O4 exhibits the strongest emission at 419 nm corresponding to the 2D15/24I9/2 transition of Nd3+ ions. What is more, Nd3+:SrY2O4 can be excited effectively by 824 nm light, which matches well with the commercial 830 nm diode laser. When excited with 824 nm, the strongest fluorescence peak is located at 1083 nm with a wide bandwidth of about 90 nm. Compared with that at 8~K, the bandwidth in the fluorescence spectrum at 300 K is broadened because of the homogeneous broadening induced by the increase of temperature. Additionally, the peaks corresponding to the 4F3/24I11/2 transition are split into two groups at 8~K, which results from the two non-equivalent sites of Nd3+ ions. Compared with Nd3+:YAG, Nd3+:SrY2O4 has more potential applications in the tunable and ultrashort lasers. The fluorescence lifetime of the 4F3/24I11/2 transition of (3 at.%) Nd3+:SrY2O4 is 281.7 s, which shows slight concentration quenching compared with that of (0.5 at.%) Nd3+:SrY2O4. The fluorescence lifetime of (3 at.%) Nd3+:SrY2O4 is much longer than that of (0.6 at.%) Nd3+:YAG which is beneficial to the energy storage. In conclusion, the wide emission band and the long decay time of 1.08 m indicate that Nd3+:SrY2O4 is a very promising new-wavelength and ultrashort laser material pumped by laser diode.