Synthesis And Luminescent Mechanisms Of (Halogen) Borate Phosphors For White LED

White light-emitting diodes（LEDs） are considered as the new generation of illumination source owing to their numerous advantages such as long lifetime, energy saving, mercury-free, etc. Achieved by combination of a blue emitting diode with a yellow phosphor Y3Al5O12: Ce³⁺ is best known which was fabricated firstly by Nichia Chemical Co. Y3Al5O12: Ce³⁺ has a high quantum efficiency and high thermal stability, however, the lack of red-emitting component leads to a low color rendering index（CRI） of the white LEDs（< 80）. There are several ways to obtain a high CRI value, for example, the combination of a near-UV chip with tricolor phosphors, or a blue-emitting chip combined with green/yellow and red phosphors with strong absorption in the near-UV and/or blue region. Therefore, it is very important to search for high efficiency phosphor that has a strong absorption in the near UV or blue light region.In this thesis, Ca₅（BO₃）₃F was selected as the host. The luminescent properties of phosphors single-doped with Ce³⁺, co-doped with Ce³⁺, Tb³⁺, and co-doped with Ce³⁺, RE³⁺, Mn²⁺ were studied in detail. The relationships between the properties such as PLE and PL, energy transfer and crystal structure were analyzed, and the following results were obtained:1)Ca₅（BO₃）₃F: Ce³⁺ phosphors exhibited purple-blue light emission peaking at 392 nm, with a strongest excitation band at 360 nm, which belongs to the Ce³⁺ in Ca（2） site.2)In Ca₅（BO₃）₃F: Ce³⁺, Tb³⁺ phosphors, the excitation energy of Ce³⁺ can be transferred to Tb³⁺ effectively, the co-doping of Tb³⁺ leads the appearance of green emision of Ce³⁺ in Ca（1） site.3)In Ca₅（BO₃）₃F: Ce³⁺, RE³⁺, Mn²⁺ phosphors, the energy of Ce³⁺ could not transferred to Mn²⁺ effectively, while the introduction of RE³⁺ enhances the emitting of Mn²⁺ significantly. The key factor that leads to the enhancement of Mn²⁺ emission is the increase the amount of Mn²⁺ on Ca（2） site with the introduction of RE³⁺.4) Eu³⁺ can’t be reduced in Ca₅（BO₃）₃F under the reducing atmosphere, but can be reduced in Sr₃B₂O₆ under the same conditions. The reason may be due to the difference in atomic sizes: Eu³⁺ < Ca²⁺ < Eu²⁺ < Sr²⁺.