Synthesis and up-conversion luminescence of Yb3+/Er3+/Tm3+ doped Ca9Y(PO4)7
Abstract
Samples of Ca9Y(PO4)7 co-doped with Yb3+/Er3+, Yb3+/Tm3+, or Yb3+/Er3+/Tm3+ have been synthesized through two different routes, i.e. a modified hydrothermal method, followed by annealing in air at 850 °C and a solid-state reaction. The results of SEM and TEM show that the particle size of the samples synthesized by the solid state reaction method is about several micrometers, while that of the sample synthesized by the modified hydrothermal method is around 180 nm. The up-conversion luminescence of samples is studied as a function of different Yb3+, Er3+, Tm3+ ion concentrations and laser powers. Under 980 nm laser excitation, samples of Yb3+/Er3+ co-doped Ca9Y(PO4)7 generate green and red emissions, while samples co-doped by Yb3+/Tm3+ generate blue and red emissions. The red emission is most intense in Yb3+/Er3+ co-doped samples, while blue emission is predominant in Yb3+/Tm3+ co-doped samples. The main mechanism that allows for the up-conversion observed in Yb3+/Er3+, Yb3+/Tm3+ or Yb3+/Er3+/Tm3+ doped Ca9Y(PO4)7 is attributed to the energy transfer among Yb3+ and the various Er3+/Tm3+ ions in excited states.