Preparation And Properties Of Rare Earth Ions-doped Phosphate Luminescent Materials

Rare earth luminescent materials plays a key role in the improvement of living standards and science and technology.The luminescent materials which the rare earth ions were used as an activator were greatly affected by the matrix.PO₄^3-in phosphates can effectively absorb the photon energy of ultraviolet and vacuum ultraviolet,so that the energy can efficiently transferred to the rare earth activated ions.That is,there are wide and strong excitation bands in the ultraviolet and vacuum ultraviolet regions.Therefore,phosphates can be used as an ideal matrix material.In this paper,Ca₉La?PO₄?₇,Ca₉Gd?PO₄?₇,BiPO₄ and Zn₃?PO₄?₂ were chosen as the matrix materials,a series of Eu³⁺,Tb³⁺,Dy³⁺doped Ca₉La?PO₄?₇,Ca₉Gd?PO₄?₇,BiPO₄ and Zn₃?PO₄?₂ luminescent materials were prepared.The crystal structure and the luminescent properties of the samples were characterized by XRD?IR and fluorescence spectrum.Eu³⁺doped Ca₉M?PO₄?₇?M=La,Gd?red phosphors,Tb³⁺doped Ca₉La?PO₄?₇ green phosphors and Dy³⁺,Eu³⁺doped Ca₉M?PO₄?₇?M=La,Gd?white phosphors were synthesized by a sol-gel method.The results show that rhombohedral phase Ca₉M?PO₄?₇?M=La,Gd?was formed when the pH was equal to 2 and the calcination temperature was between 700?and 900?.The excitation and emission spectrum of the samples shows that Ca₉M?PO₄?₇:Eu³⁺?M=La,Gd?have intense red light emission at 613 nm under395 nm near-UV excitation;Ca₉La?PO₄?₇:Tb³⁺have green light emission at544 nm under 378 nm near-UV excitation;Ca₉M?PO₄?₇:Dy³⁺,Eu³⁺?M=La,Gd?exhibit white luminescence under 388 nm near-UV excitation.By the comparison of the emission spectrum of Ca₉M?PO₄?₇:Eu³⁺?M=La,Gd?and MPO₄:Eu³⁺?M=La,Gd?,it can be seen that Ca₉M?PO₄?₇:Eu³⁺?M=La,Gd?shows better red emission color purity with excellent performance.Through the comparison of the emission spectrum of Ca₉La?PO₄?₇:Eu³⁺and Ca₉Gd?PO₄?₇:Eu³⁺,we can know that Ca₉La?PO₄?₇:Eu³⁺have a better prospect of application with greater luminescent intensity and better red emission color purity.Eu³⁺,Tb³⁺doped BiPO₄ luminescent materials were synthesized by a solvothermal method.With the extension of solvothermal time?3 h³6 h?,the phase of the samples changes from hexagonal to monoclinic.It was found that the phase of the sample was hexagonal when the solvothermal temperature was 140?.However,a mixture of hexagonal and monoclinic was observed when the solvothermal temperature was gradually increased to200?.Besides,the increase of the PO₄^3-concentration will also lead to the changes from hexagonal phase BiPO₄ to monoclinic phase BiPO₄.The excitation and emission spectrum of the samples shows that BiPO₄:Eu³⁺mainly have orange red light emission at 593 nm under 395 nm near-UV excitation,which corresponds to the magnetic dipole ⁵D₀?⁷F₁ transition;BiPO₄:Tb³⁺have green light emission at 544 nm under 378 nm near-UV excitation,which corresponds to the ⁵D₄?⁷F₅ transition.Eu³⁺doped Zn₃?PO₄?₂ luminescent materials were synthesized by a coprecipitation method.When the pH was less than 4,Zn₃?PO₄?₂ can not be obtained;when the pH was between 4 and 8,a pure?phase Zn₃?PO₄?₂ was formed;however,when the pH was greater than 8,there were some impurities generated.A mixture of?phase Zn₃?PO₄?₂ and?phase Zn₃?PO₄?₂ was observed when the calcination temperature was between 500?and 700?;when the calcination temperature was increased to 800?,a pure?phase Zn₃?PO₄?₂ was obtained.The excitation and emission spectrum of the samples shows that?-Zn₃?PO₄?₂:Eu³⁺mainly have orange red light emission at 593 nm under 396 nm near-UV excitation,which corresponds to the magnetic dipole⁵D₀?⁷F₁ transition.In this paper,common rare earth ions Eu³⁺,Tb³⁺,Dy³⁺were chosen as activators,Ca₉La?PO₄?₇,Ca₉Gd?PO₄?₇,BiPO₄ and Zn₃?PO₄?₂ were chosen as the matrix materials,a series of phosphors with excellent luminescent performance were prepared with suitable methods.It has enriched the research contents of rare earth luminescent materials and provided some basic information for further study of phosphate luminescent materials.