The VUV Luminescence Properties Of M₂SiO₄:RE (M=Mg, Sr, Ba, RE=Tm～(3+),Tb～(3+))

Now, more and more scholars pay their attention to the phosphors used for PDP (plasma display panel). Silicate phosphors are promising as candidates of host materials for the new VUV phosphors with various crystal structures and high chemical stability. In this article, it was attempted to prepare rare ion doped M2SiO4 phosphor by the solid-state reaction and their luminescent properties under VUV were investigated.The X-ray powder diffraction data of M₂SiO₄: RE (M=Mg, Sr, Ba, RE=Tm³⁺, Tb³⁺) is in agreement of JCPDS standard card (87-0061, 39-1256, 26-1403), which indicates that the doped rare ion have little influence on the structure of luminescent host. It indicates that single-phased M₂SiO₄ phosphor can be obtained in such synthesis process.The VUV excitation spectrum under 457nm of M₂SiO₄: Tm³⁺ (M=Mg, Sr, Ba) shows two peaks at about 170nm and 190nm and a broad excitation band from 211nm to 300nm. The former can be assigned to the absorption of the host lattice, which is shifted towards longer wavelengths as the radius of alkali earth ion in M site increases (Mg²⁺＜Sr²⁺＜Ba²⁺). The latter corresponds to the O-Tm³⁺ charge transfer transitions, which is weakened as the radius of alkali earth ion in Re site increases. In the VUV emission spectra of M₂SiO₄: Tm³⁺ (M=Mg, Sr, Ba) under 161nm excitation, The emission peaks at 357nm, 459nm and 478nm are corresponding to ¹D₂→³H₆, ¹D₂→³H₄ and ¹G₄→³H₆ transitions of Tm³⁺, respectively.The VUV excitation spectrum of Ba₂SiO₄: Tb³⁺ under 545nm consists of two broad bands peaked at 186nm and 238nm, respectively. The former can be assigned to the absorption of the host lattice, and the latter corresponds to the O- Tb³⁺ charge transfer transitions, in the vuv emission spectrum of Tb³⁺ under 161nm excitation, the emission peaks at 486 nm, 545 nm, 589 nm and 623 nm corresponds to the ⁵D₄→⁷F_j(J=6, 5, 4, 3) transitions of Tb³⁺. The emission spectra of Ba₂SiO₄: Tb³⁺ have revealed that an intense and sharp (545 nm) green emission from Tb³⁺ (⁵D₄—⁷F₅).In the XRD parttens of Ba_2-xSr_xSiO₄: Tb³⁺ when X=0, the XRD partten of Ba₂SiO₄: Tb³⁺ accords with the JCPDS standard card of 26-1403. The diffraction peaks of Ba₂SiO₄ are weakened as the value of X increases and the diffraction peaks of Sr2SiO4 is stronger as the value of X increases. In the VUV excitation spectrum of Ba_2-xSr_xSiO₄: Tb³⁺ under 545nm, the absorption intensity of the host lattice, which is about 186nm and 238nm, is weakened as x increases. The absorption peak is shifted towards longer wavelengths. The VUV emission spectrum of Ba_2-xSr_xSiO₄: Tb³⁺ consists of four peaks at 491nm, 545nm, 589nm, 624nm, respectively. They are duo to the transitions of Tb³⁺(⁵D₄-⁷F_j, J=6, 5, 4, 3), and the excitation of 545nm is the strongest. The emission intensity is different of the change of x in the doped same activation ion, but it doesn't show the disciplinarian change as the ratio of Ba/Sr increases. The emission intensity of Ba_0.4Sr_1.6SiO₄: Tb³⁺ is the strongest.