K_2SiF_6∶Mn^(4+)荧光粉湿热环境下的劣化行为

Degradation Behavior of K_2SiF_6∶Mn^(4+) Phosphors Under Heat-moisture Conditions

研究了白光LED用K_2Si F_6∶Mn^(4+)红色荧光粉湿热环境下的发光性能劣化规律及机理。结果表明,环境中水汽的侵蚀可导致K_2Si F_6∶Mn^(4+)荧光粉发光性能劣化,且温度升高可加剧该劣化过程。85%湿度/70℃下处理6 h,K_2Si F_6∶7%Mn^(4+)荧光粉相对亮度降至初始值的25%。荧光粉中Mn^(4+)含量越高,湿热条件下的性能劣化越显著。基于湿热处理前后荧光粉的XRD、表面形貌以及光学性能的对比分析,发现湿热环境下K_2Si F_6∶Mn^(4+)荧光粉的劣化主要是由于表面水汽侵蚀产物强吸收400~700 nm的可见光,降低荧光粉的激发效率以及再吸收荧光粉的发射光。水热后处理可使K_2Si F_6∶Mn^(4+)荧光粉颗粒尺寸增大,结晶性提高,从而显著改善其耐水性。85%湿度/70℃下处理6 h,水热后处理K_2Si F_6∶7%Mn^(4+)荧光粉的相对亮度仍可保持初始值的80%。

Herein,degradation behavior and mechanism of K2SiF6∶Mn^4＋（KSFM） red phosphors in hot and humid environment were investigated. The attack by moisture can induce the emission intensity of KSFM phosphors to decrease and limit their applications in white LEDs. The moisture degradation of KSFM would be aggravated at higher temperatures. Under 85% humidity and 70 ℃ for6 h,the relative brightness of K2SiF6∶ 7% Mn^4＋ falls to 25% of the initial value. With the increase of Mn^4＋ contents in KSFM phosphors,more significant emission intensity decrease in hot and humid environment is obtained. Based on the comparative analysis of XRD,morphology and optical properties of KSFM phosphors before and after heat-moisture treatments,the degradation of KSFM can be attributed to the reaction between environmental moisture and phosphors. The reaction products,which are located on the particle surface and exhibit broad absorption bands between 400 and700 nm,can decrease the excitation efficiency and re-absorb the emitted light of phosphors,lead to the degradation of KSFM phosphors in hot and humid environment. It is also found that the hydrothermal post-treatments result in the increase of the particle size of phosphors and the improvement of their crystalline,and thus significantly enhance the moisture resistance of KSFM phosphors. Thehydrothermally post-treated K2SiF6∶ 7% Mn^4＋ phosphor can retain 80% of the initial brightness after exposure a hot and humid environment（85% humidity and 70 ℃） for 6 h.