Upconversion luminescence properties of Y2SiO5: Er3+,Yb3+, Tm3+ synthesized by co-precipitation method

series of up-conversion luminescence materials of Y1.98-2xYb2xEr0.02SiO5 (0. 00 <= x <= 0. 15) and Y1.736Yb0.24Er0.02 Tm0.004SiO5 were synthesized by co-precipitation method. The absorption spectra from 400 to 1600 nm of Y1.98-2x.Yb2xEr0.02 SiO5 (x = 0.00, 0. 08) were compared, and the up-conversion emission spectra of all samples were investigated when excited by 976 nm opo laser. The decay curves of Er3+4S3/2 (F-4(9/2)) -> I-4(15/2) , Tm(3+1)G(4) -> H-3(6), as well as the relationship between the blue up-conversion emission intensity and pumping power were measured, consequently, the possible up-conversion luminescence mechanisms of Er3+,Tm3+ in Y2SiO5 were discussed. The results show that X2-type monoclinic Ln(3+) (Ln(3+) = Er3+, Yb3+ ,Tm3+) co-doped Y2SiO5 phosphors have been synthesised under relatively low temperature of 1250 degrees C, and the absorption intensity and bandwidth are remarkably increased by Yb3+ sensitizing around 976 nm. Up-conversion emission spectra has been analyzed and the results suggest that both the green and red lights increase first and then decrease with the increase of the Yb3+ doping concentration. However, the concentration quenching of the red light emission is higher, due to the forward (ETU3) and back (ETU4) energy transfer between Yb3+ and Er3+ ions; the blue emission occurs mainly through phonon-assisted energy transfer between Yb3+ and Tm3+ ions, which is a three photon absorption process.