Luminescent Properties Of Rare-earth Ion-doped Allomorphism Phosphor Materials

Rare earth doped luminescent materials have a wide range of applications in the fields of display,illumination and detection.The luminescent properties of the material are closely related to the composition and structure of the host.Polycrystals with similar chemical composition but different crystalline structure may provide variable local crystal environment for rare earth ions,ruslting in tunable luminescent properties.In this thesis,three types of polycrystals,Ca₃?PO₄?₂,Na₂Ca₄?PO₄?₂SiO₄,LiZr₂?PO₄?₃ were selected as the luminescent host.Eu²⁺doped polymorphic luminescent materials were synthesized by finely controlling the crystal form of the host.The luminescent properties and their differences of Eu²⁺ions in polymorphic phosphors were investigated and the relationship between the luminescent properties and host structure was dissucssed.The obtained results were summarized as follows:?1?Ca₃?PO₄?₂ polycrystal was selected as the luminescent host to prepare Eu²⁺doped?/?"-Ca₃?PO₄?₂ phosphors by controlling the temperature of the solid-phase reaction.The effect of Eu²⁺doping concentration and Sr²⁺solution content on the luminescence properties of???-Ca₃?PO₄?₂:Eu²⁺and?-Ca₃?PO₄?₂:Eu²⁺phosphors were investigated respectively.When Eu²⁺was incorporated in the hosts,the Eu²⁺mainly occupies the Ca?4?lattice position in the?phase,while the Eu²⁺doping concentration increasing,resulting in the red-shift of emission.Additionally,Sr²⁺solid-soulution would aslo lead to the change of Eu²⁺accommodation from Ca?4?to Ca?1?and Ca?2?,then resulting in the red-shift of luminescence wavelength.?2?Eu²⁺doped?/?-Na₂Ca₄?PO₄?₂SiO₄ phosphors were synthesized by controlling crystal form Na₂Ca₄?PO₄?₂SiO₄ polycrystal through adding B₂O₃ flux.The variation of temperature in the range of 1200-1300?did not change the crystal structure of Na₂Ca₄?PO₄?₂SiO₄ mateirals.With the increase of the addinig content B₂O₃ flux,the pahse component of samples transformed from the?/?mixed phase to the?pure phase.As a result,the luminescent of the phosphors changed with the transformation of phase component.?3?Three types of ?'-??-??'-LiZr₂?PO₄?₃:Eu²⁺phosphors were synthesized by controlling the temperature of solid phase reaction basing on LiZr₂?PO₄?₃ polycrystal.With the increasing of the doping concentration of the activator Eu²⁺,the effect of the solid phase reaction temperature on the crystal structure of the LZP matrix becomes smaller.The coexist phenomenon was detected in LiZr₂?PO₄?₃ host and more obvious in the low Eu²⁺concentration doping samples.In addion,the increase of activator doping concentration induces the transfer of luminescent centers from one occupied site to another site,resuling in the variation of Eu²⁺emission wavelength.