Investigation On The Optical Properties And Preparation Of Three-convetred Borate Phosphors

This paper develops several novel borate phosphors for white LEDs due tothe characteristics of the advantageous luminescent properties, easy preparation, lowcalcining temperature, etc. The crystal field theory is applied to research theinfluence of the lattice suroundings occupied by the activators on the luminescentproperties of the activators. The concrete contents are listed below.The novel blue-emitting phosphors under ultraviolet light excitation, weresuccessfully synthesized, such as novel BaKBP₂O₈: Eu²⁺, Ba₃B₆Si₂O₁₆: Eu²⁺, andLiSr₄（BO₃）₃: Ce³⁺phosphors. The excitation peaks of the three novel phosphors arelocated at346,360, and350nm, respectively. They exhibited blue emission peakingat443,445, and420nm, respectively. The full widths at half maximum of theiremission spectrum are around90,63, and90nm, respectively. Based on the researchof concentration quenching mechanism of the doped ions, the resonance-type energytransfer mechanism between the identical activators is dominant by electricdipole-dipole interaction. The crystal field theory is used to research theluminescence properties of the activators at different luminescence centers. The Ce³⁺ions occupied two different lattice sites, which resulted in four different emissionpeaks of402,436,468, and515nm, respectively.The novel green-emitting phosphors under ultraviolet light excitation, weresuccessfully synthesized, such as novel BaZn（BO₃）F: Eu²⁺, BaZn₂（BO₃）₂: Eu²⁺phosphors. The excitation peaks of the two novel phosphors are located at375and365nm, respectively. They exhibited green emission peaking at500and505nm,respectively. The full widths at half maximum of their emission spectrum are around132and105nm, respectively. Based on the research of concentration quenchingmechanism of the doped ions, the resonance-type energy transfer mechanismbetween the identical activators is dominant by the electric dipole-dipole interaction.The novel yellow-emitting Ba₂LiB₅O₁₀: Eu²⁺and red-emitting LiSr₄（BO₃）₃: Eu²⁺phosphors under ultraviolet light excitation, were successfully synthesized. Theyexhibited excitation peaking at365and420nm, respectively, and gave emission peaking at587and612nm, respectively. The full widths at half maximum of theiremission spectrum are around152and160nm, respectively. They both have goodcolor stuaration. According to the research of concentration quenching mechanism ofthe doped ions, the resonance-type energy transfer mechanism between the identicalactivators is confirmed to be the electric dipole-dipole interaction. The crystal fieldtheory is used to research the luminescence properties of the activators. The resultsindicated that the occurance of the two different emission peaks of580and646nmcomes from the occupancy of two lattice sites by Eu²⁺ions in the LiSr₄（BO₃）₃hostlattice.White light was observed from the Ce³⁺/Eu²⁺co-activated LiSr₄（BO₃）₃: phosphorswith the CIE chromaticity coordinate （x, y） of （0.34,0.30） by adjusting the relativeratio of Ce/Eu. Based on the photoluminescence properties of the samples, themechanism of the energy tranfer from Ce³⁺to Eu²⁺was analyzed in detail.