The Synthesis And Luminescence Property Of Eu²⁺ ,Ce³⁺ Doped CaSi₂O₂N₂ Phosphor

A series of CaSi₂O₂N₂:Eu²⁺ powders have been synthesized through solid-state reaction method under N2-H2 atmosphere. The formation and chemical reaction process was deduced from XRD patterns and PL spectrums of the powders. The crystal structure and fluorescence properties of Ca_1-xEu_xSi₂O_-δN2+2/3δhave been systematically investigated (x=0, 0.005, 0.01, 0.02, 0.04, 0.05, 0.08, 0.1, 0.2;δ=0, 1). Red-shift and concentration quenching have been deeply discussed. HF treatments have been carried out to improve the microstructure and PL properties of the phosphors.(Eu²⁺, Ce³⁺) co-doped CaSi₂O₂N₂ phosphors have also been prepared, and white light is obtained under UV excitation (330nm) due to Ce³⁺→Eu²⁺ energy transfer mechanism.The experiment results and analysis shows that: single phase CaSi₂O₂N₂:Eu²⁺ (δ=0) powders can be formed during 1200°C to 1500°C, the holding time (1h to 12h) of the above reaction temperatures contribute little to the crystal phase while influence the luminescence properties evidently; High N/O (δ=1) may broaden the excitation spectrum band due to strengthen of the crystal field strength around the Eu²⁺ in the phosphor lattice. As increasing the Eu²⁺ content, the emission spectrum of the phosphor show red-shift and concentration quenching (x=0.02) which due to the interaction between different Eu²⁺ diploes. CaSi₂O₂N₂:Eu²⁺ shows single broad band emission under UV-NUV excitation, centering at 530-550nm. HF treatment process could purify the phase and microstructure, improve the photoluminescence, increase the emission intensity, and the emission spectras change to longer wavelength band.Introducing of Ce³⁺ caused increase of emission intensity of Eu²⁺, while increasing Eu²⁺ concentration the emission intensity of Ce³⁺ decreases due to energy migration over Eu²⁺ ions in the lattice. Resonance-type energy transfers from Ce³⁺ to Eu²⁺ were discovered by directly overlapping the Ce³⁺ emission spectra and the excitation spectra of Eu²⁺.The mechanism of non-radiative energy transfer from Ce³⁺ to Eu²⁺ is found to be electric dipole-dipole interaction. The CIE chromaticity coordinate of (Eu²⁺, Ce³⁺) co-doped CaSi₂O₂N₂ phosphors vary form (0.167, 0.05) to (0.349, 0.521). Optimization of Eu²⁺ concentration was carried out to produce white light in the prepared Ca0.98-xEuxCe0.01Li0.01Si2O2N2.According to the principle of energy transfer, we demonstrated CaSi₂O₂N₂:Ce³⁺/Eu²⁺ with blue and yellow emission bands exhibited a great potential as a phosphor for NUV-blue light-emitting diodes.