Study On The Synthesis And Upconversion Properties Of Tm/Ho/Yb Doped12caO·7Al₂O₃

12CaO·7Al₂O₃（C12A7） doped with rare-earth ions was a upconversionluminescence material which has a broad application. Tm³⁺, Ho³⁺, Yb³⁺dopedC12A7samples were prepared by solid state method, which was synthesisd bysintering6h under1100oC. The XRD results showed that there was no effect of thedopant ions on the crystal lattice of C12A7.A series of C12A7: Tm³⁺, Yb³⁺samples with1mol%Tm³⁺ions and differentconcentration of Yb³⁺ions were prepared. Under980nm excitation, the blue and redupconversion emission centered at475nm and650nm observed in C12A7: Tm³⁺,Yb³⁺samples, which arised from the1G4â†'³H₆and¹G₄â†'³F₄transition of Tm³⁺ion,respectively. The result showed that the intensity of upconversion luminescence andthe ratio of blue/red were changed with the Yb³⁺ions concentration.. The pumpdependence indicated that the blue and red upconversion emission resulted from thetwo and three-photon process. Combined with the energy structure of Tm³⁺and Yb³⁺ions, the blue and red upconversion mechanism were analyzed.C12A7: Ho³⁺, Yb³⁺samples with1mol%Ho³⁺ions and different concentrationof Yb³⁺ions were prepared. The upconversion emission spectra suggested that the⁵F₄/⁵S₂â†'⁵I₈of Ho³⁺ion emited green luminescence and the⁵F₅â†'⁵I₈transitionemited red luminescence, which centered at548nm and662nm, respectively. Theintensity of upconversion luminescence and the ratio of red/green were changedwith Yb³⁺ions concentration. The pump dependence showed the green and redupconversion emissions were populated by two-photon process, and theupconversion mechanism was analyzed.The upconversion luminescence properties of C12A7: Tm³⁺, Yb³⁺, Ho³⁺samples were studied by orthogonal experiments. The experimental results indicatedthat the concentration of rare-earth ions and the interaction between rare-earth ionscould affect the intensity of upconversion luminescence and the ratio betweendifferent upconversion emisions. C12A7:0.7mol%Tm³⁺,0.5mol%Ho³⁺,4.0mol%Yb³⁺sample emited write emission, and the CIE coordinate （0.32,0.34）closed to the white emission center（0.33,0.33）. The pump dependence suggestedthat the blue upconversion emissions was populated by three-photon process, thegreen was two-photon process, the red was two-and three-photon processes. Studies on the upconversion mechanism showed that the blue, green and red upconversionemissions were attributed to the continuous energy transfer process.