This paper is aimed at explaining the effects of Tb 3+ concentration on structure and luminescence properties and clarifying the concentration quenching mechanism of Tb 3+ . The lattice of BaF 2 decreases with the increase of Tb 3+ ions concentration. The emission spectrum of BaF 2 :Tb 3+ consists of blue emission band and green emission band and corresponds to the transition of 5 D 3 → 7 F J (J = 0, 1, 2, 4, 5, 6) and 5 D 4 → 7 F J (J = 2, 3, 4, 5, 6) of Tb 3+ . The optimum concentration of Tb 3+ is 4 mol%, and the concentration quenching mechanism of Tb 3+ can be interpreted by the dipole-quadrupole (d-q) interaction.
The Sr2B2O5:Eu2+ phosphor was synthesized by high-temperature solid state reaction. The crystal structure of Sr2B2O5:Eu2+ phosphor is monoclinic system with space group of P21/a(14). Due to Eu2+ ion doping, the lattice parameters and unit cell volume decreased. The luminescence spectrum is a broad luminescence band peaking at 468 nm and 478 nm, which corresponds to the transition of 5d-low energy state in Eu2 and Eu1 to the ground state. The excitation spectrum is at UV region less than 264 nm corresponding to the band gap transition of borate host. The low energy level of 5d-band locates 20921 cm-1, the band width is 1 eV. The electronegativity of O2- anions around Eu1 and Eu2 is 3.147 eV and 3.326 eV respectively, which determines the split of 5d energy level.
Eu2+ doped Sr3B2O6 yellow phosphor for warm white LED was synthesized by high temperature solid-state method. The structure and optical properties of Sr3B2O6 : Eu2+ were studied. Results indicate that Sr3B2O6 : Eu2+ has a rhombohedral crystalline structure. The excitation spectrum of phosphor is a wide-band spectrum mainly peaking at 469 nm, which is suitable for GaN -based blue light LED excitation. The luminescent spectrum of phosphor exhibits a broad emission band centered at 566 nm, corresponding to the typical 4f65d1–4f7 transition of Eu2+ . Guass fitting shows the main emission peak is at 575 nm, which is identical with the dominant wavelength of the yellow phosphor. The CIE chromaticity coordinate of white LED is (x = 0.389, y = 0.419). The LED reveals warm tone and the relevant color temperature of that is 4044 K. The luminescent efficiency of White LED reaches 18l m/W, which is higher than reported.
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