Hydrolytic resistant performance evaluation for Y 3 A1 5 O 12 : Ce 3+ yellow phosphor used in white LED packaging

Due to its low cost and high efficiency, the blue LED chip covered with the $\mathrm{Y}_{3}\mathrm{A}1_{5}\mathrm{O}_{12}:\mathrm{C}\mathrm{e}^{3+}$ (YAG) yellow phosphor has become the mainstream of current white LED packaging. However, phosphors are often susceptible to degradation under high temperature and high humidity condition, which directly affects the optical and color stability of white LED package. In this study, the hydrolysis reaction kinetic of YAG phosphor was firstly investigated by using a water immersion test, and its hydrolysis mechanism was then revealed by characterizing phosphor’s emission spectrum, photothermal property, crystal structure, microscopic surface morphology and chemical element composition. Finally, the hydrolysis effect of YAG phosphor on the mechanical properties of phosphor/silicone composites was investigated. The results show that: 1) the in situ monitored electrical conductivity at $30-60^{\circ}\mathrm{C}$ shows that the hydrolysis reaction rate of YAG yellow phosphor reaches to highest at $50^{\circ}\mathrm{C};2$) the lowest emission intensity and highest surface temperature of the phosphor treated at $50^{\circ}\mathrm{C}$ water immersion test confirm the most serious hydrolysis reaction happened at that condition; 3) both the Young’s modulus and tensile strength of phosphor/silicone composite increase after adding the hydrolyzed phosphor.