Study On The Synthesis Of Borates Phosphors Used For White LED And The Luminescent Properties

The synthesis and characterization of phosphors used for white LED were paid more attention with the extension of application and the development of preparation technology in white LED. Especially, the properties of phosphor excited by blue or UV light affect directly the color rendering of white LED. Because of limitation of red phosphors applied nowadays, it's necessary to find a new type of red phosphors for white LED.A series of stable red phosphor (R, Eu)_xBa_1-2xB₂O₄(R=Li, Na, K), (R, Eu)x Sr1-2x B₂O₄ (R=Li, Na, K) and (R, Eu) xCa1-2xB2 O4(R=Li, Na, K) based on molybdates was prepared by solid-state process. The factors that affect their luminescent properties, such as concentration of Eu³⁺ and the reactiontemperatures were studied.The excitation spectra of MB₂O₄:Eu³⁺(M=Ba,Sr,Ca) include a broad range from 250 nm to 500 nm, which have three excitation peaks at 296 nm, 395 nm and 465nm; the emission spectra are composed of many sharp lines ranged from 350⁷50nm, and the peaks at 616 nm was the strongest lines which are corresponded to transition of 5D0-7F1, 7F2, 7F3, 7F4. The excitation spectra show effective absorption wave lengths at ultraviolet (UV)(395nm) and blue (465nm) corresponding to the f-f transition of Eu³⁺ which are matched well with the wave-lengths of commercial GaN based LED, thus, the phosphor may be a better candidate for red component for white LED.As we sueved the dipole-dipole interaction is the major mechanism for concentration quenching of the central Eu³⁺ emission.The different charge compensators influence the luminous characteristic of samples phosphors. The emitting intensity of the phosphors changes with different charge compensators These phenomena may be due to the fact that the ionic radius of charge compensators is similar to matrix cations, so that charge compensators can substitute matrix cations easily without disturbing the crystal lattice. While the addition of charge compensators results in the distortion of the crystal structure because of a big discrepancy between the ionic radius of charge compensators and matrix cations, and then impacts on the luminous properties.