Enhanced green up-conversion luminescence for Er3+, Y3+ co-doped SrF2 phosphors under 808 nm excitation

A series of SrF 2 phosphors co-doped with Er 3+ and Y 3+ possessing regular polygon shapes were fabricated after calcination as-synthesized particles at 600 °C for 2 h. the crystal structure and morphology of the Er, Y:SrF 2 phosphors were identified. By incorporating the non-active Y 3+ ions as buffers into Er:SrF 2 phosphors, intense green up-conversion luminescence with modulating emission colors from reddish-yellow towards the greenish area is achieved. The two-photon up-conversion mechanism was also identified by the quadratic dependence between the luminescence intensities and 808 nm excitation source powers. The up-conversion luminescence characteristics indicate that Y 3+ buffers significantly enhance the 2 H 11/2 / 4 S 3/2  →  4 I 15/2 transitions, leading to an approximately five-fold increase in the luminescence intensities ratio R(g/r) of the green to red emissions in Er:SrF 2 phosphors.