Investigation Of Effects On Micro-structure And Luminescence Properties Of YAG: Ce Substituted By Cations

Aluminate based luminescent materials activated by rare earth ions are widely used Because of their high efficiency, stable chemical properties and lower cost et al. In recent years, with the advantages such as small size, fast response, long life and no pollution, white light-emitting diodes (WLEDs) become the new generation lighting sources. At present, the WLEDs Combined blue LED and yellow YAG:Ce phosphor become mainstream of the market and obtain a wide range of applications. The serious objection of phosphors on temperature related luminescence intensity decline, color coordinates drifting et al. lead to degradation of device performance which remains one of key issues under improvement.In this paper, we discussed thermally-induced decay mechanism and method for improving luminescent properties. By cations doping and replacement, we try to change the host microstructure in order to modulate luminescence peak position and improve the non-radiative transition probability. The main results are as follows:[0]1.The effects of structural change by doping Gd³⁺ on Ce³⁺ are discussed. The results show that Gd³⁺ is priority to replacing Y³⁺ because of the similar of the two cation radius. The slight enlargement of crystal cell and the lowers energy level of 5d made the luminescent peak of Ce³⁺ red-shift.As the results, the color render of WLED is compensated. The flux CaCO3 improved the phosphors with better dispersion and easier crush. By adding 0.5mol of CaCO3, the luminous intensity of sample is 1.5 times than without CaCO3 added[0].2. The effect of Gd³⁺ concentration on(Y_2.94-xGd_xCe_0.06)Al₅O₁₂ is investigated at room temperature(RT). The results show that the peak wavelength moves from 530nm to 550nm by addition of Gd³⁺ from 0 to 0.6mol. and the peak intensity firstly increases and then reduces because energy transfer play a major role when doped small amounts of Gd³⁺ and concentration quenching is dominant when more Gd³⁺ is doped. The experiment results proved that the phosphors remain structure of Y3Al5O12 phase when lower than 0.6mol Gd³⁺ doping and optimal luminescent intensity happens at 0.3mol Gd³⁺ doping.3. The temperature dependence of (Y_2.94-xGd_xCe_0.06)Al₅O₁₂ phosphors were investigated. The peak intensity shows the normal red-shift with broadening bandwidth and decreasing emission intensity as the temperature increasing. With the increasing of doped Gd³⁺, the declining rate and dilated trend are aggravated.[0] The mechanism could be owed to enhancement of energy level splitting. and non-radiative transition strengthens due to interaction between electrons and phonons.4.The Si⁴⁺ ions replaced SiO₂-YAG: Ce phosphors and ceramic are prepared by the composite method. X-ray diffraction, scanning electron microscopy and fluorescence spectrometer. Results indicated that the luminescence properties of samples improved obviously. Temperature related spectra measurement showed that the thermal stability increased 22% than that of YAG: Ce phosphor by 1.0mol concentration of SiO₂ .