Properties Of Luminescent Materials With β-Ca₃（PO₄）₂Structure

The luminescent materials doped with rare earth are widely used in illumination,display technoligies and detection. The investigations of luminescent materials have agreat importance as they play a decisive role in the luminescence properties of thecompact fluorescent lamp and LEDs. Phosphors with the matrix of Phosphate andVanadate have been extensively investigated due to their good thermal stability, lowtemperature synthesis and good luminescence properties under UV irradiation. In thispaper, we select the compounds Ca₉ZnLi（PO₄）₇, Ca₉Ln（PO₄）₇（Ln=Y, Gd） andCa₉A（VO₄）₇（A=Bi, La, Gd, Y） with the β-Ca₃（PO₄）₂structure as the hosts, respectively.New phosphors are synthesized with the activators Ce³⁺, Tb³⁺, Mn²⁺and Eu³⁺, utilizingthe activator ions occupying different sites in the hosts and the energy transfer betweenthem. The XRD, PL and also other testing methods are used to study the impact of thesynthesis conditions and doping concentration on the structure and luminescenceproperties. Besides, their luminescent mechanism and chromaticity have been analysedand calculated.The phosphors Ca₉ZnLi（PO₄）₇: Ce³⁺, Tb³⁺(or Mn²⁺) were prepared by solid-statereaction. Both of their excitation spectra are broad bands with the peak at around320nm,and existed a resonance-type energy transfer from Ce³⁺to Tb³⁺or Mn²⁺. The criticaldistance between the activator ions were calculated. The relative intensities of green or redemission could be tuned by adjusting the dopant concentration. Green phosphorCa₉Ln（PO₄）₇: Ce³⁺, Tb³⁺（Ln=Y, Gd） exhibits blue and green emission bands was alsoprepared by solid-state reaction. As the resonance-type energy transfer from Ce³⁺to Tb³⁺existed, the sensitizer of Ce³⁺could effectively enhance the green emission of Tb³⁺. As theTb³⁺concentration increases, the PL intensity increases and no concentration quenching isobserved in the range of our experiment. Ca₉A（VO₄）₇: Eu³⁺（A=Bi, La, Gd, Y） weresynthesized by sol-gel method, and obtained the optimal synthesis conditions. Thestrongest emission intensity peaked at614nm which results from the electric dipoletransition5D0-7F2of Eu³⁺. An efficient energy transfer from VO43-group to Eu³⁺has takenplace. The Ca₉Eu（VO₄）₇phosphor has the strongest red emission in this system, and shows brighter emssion under the394nm excitation than that of the commercial phosphorY₂O₃: Eu3+, exhibits an excellent luminescence properties as the red emitting phosphorunder near-UV excitation.