Ca9R(VO4)7 : Eu3+ 发光粉的发光特性

采用高温固相法制备了Eu³⁺离子激活的Ca₉R(VO₄)₇(R = Y, La, Gd)红色发光粉,并利用荧光光谱对发光粉的特性进行研究。激发光谱中,Ca₉Y(VO₄)₇ : Eu³⁺ , Ca₉La(VO₄)₇ : Eu³⁺和Ca₉Gd(VO₄)₇ : Eu³⁺都有两个宽的VO^3-₄激发带和Eu³⁺的特征激发峰。发射光谱中,在Ca₉Y(VO₄)₇ : Eu³⁺ 和Ca₉La(VO₄)₇ : Eu³⁺中的350~550 nm范围内出现VO^3-₄的发射带,而在Ca₉Gd(VO₄)₇ : Eu³⁺中却没有观察到VO^3-₄的发射。在这三种发光粉中,Ca₉Gd(VO₄)₇ : Eu³⁺的发光强度远远高于其它两种,这是由于Gd³⁺的存在有效地使能量通过Gd³⁺ →VO^3-₄ → Eu³⁺及Gd³⁺ → Eu³⁺的两种方式进行能量传递,从而提高了Eu³⁺发光效率。

Photoluminescence Properties of Ca9R(VO4)7 (R=Y, La, Gd) Phosphors Activated with Eu3+ Ions

The red phosphors of Ca_9R(VO_4)_7:Eu~(3+)(R=Y, La, Gd) were prepared by high temperature solid state reaction method. The structures of these powders were recorded by X-ray powder diffraction. The excitation and emission spectra were recorded by F-4500 spectrofluorometer. The photoluminescence properties were investigated in this paper. The excitation spectrum of Ca_9Y(VO_4)_7:Eu~(3+) shows two broad absorption bands in the range of 200～350 nm with maximum centered at 254 nm and 320 nm, respectively. The former corresponds to CTS of VO_4~(3-) complex and the latter corresponds to an overlap of both CTS of VO_4~(3-) complex ion and Eu-O CTS band, and also displays sharp absorption lines of f-f transition of Eu~(3+) ion located at 398 nm (~7F_0→~5L_6), 467 nm (~7F_0→~~5D__2), and 538 nm (~7F_0→~5D_1), respectively. The excitation spectrum of Ca_9La-(VO_4)_7:Eu~(3+) is similar to that of Ca_9Y(VO_4)_7:Eu~(3+). In Ca_9Gd(VO_4)_7:Eu~(3+), the excitation spectrum also shows two broad bands centered at 274 nm and 331 nm, respectively,which mainly corresponds to the CTS of VO_4~(3-) complex ion. The photoluminescence spectra of Ca_9Y(VO_4)_7:Eu~(3+) and Ca_9La(VO_4)_7:Eu~(3+) exhibit broad emission of VO_4~(3-) complex ion and some sharp lines due to the transition of ~5D_J(J=0,1)→ ~7F_J (J=1, 2, 3, 4) in Eu~(3+) ion. With increasing concentration of Eu~3+ ions, the emission of VO_4~(3-) is decreased compared to the transition of ~5D_J→~7F_J (J=1, 2, 3, 4) in Eu~(3+) ion. However, the emission of VO_4~(3-) is not exhibited in Ca_9Gd-(VO_4)_7:Eu~(3+). Only the transitions of ~5D_J→~7F_J (J=1, 2, 3, 4) of Eu~(3+) ion are observed in this compound. The intensity of luminescence is observed much stronger than that of Ca_9Y(VO_4)_7:Eu~(3+) and Ca_9La(VO_4)_7:Eu~(3+) because two kinds of energy transfer processes of Gd~(3+) → VO_4~(3-) → Eu~(3+) and Gd~(3+) → Eu~(3+) are occurred. Thus, it was resulted that the luminescence efficiency of Ca_9Gd(VO_4)_7:Eu~(3+) is improved significantly.