Origin of Thermal Degradation of Sr2-xSi5N8:Eux Phosphors in Air for Light-Emitting Diodes
Origin of Thermal Degradation of Sr2-xSi5N8:Eux Phosphors in Air for Light-Emitting Diodes
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DOI：
10.1021/ja304754b
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发表时间：
2012-08-29
影响因子：
15
通讯作者：
Hintzen, Hubertus T.
中科院分区：
文献类型：
--
作者：
Yeh, Chiao-Wen;Chen, Wei-Ting;Hintzen, Hubertus T.
基于M_2Si_5 N_8：Eu（M = Sr，Ba）的橙红色发光材料由于其显色指数（CRI）的改善而被广泛用于白色发光二极管（WLED）中，所述显色指数对于暖白色光发射是明亮的。氮化物基磷光体由于其优异的热稳定性和化学稳定性而被用于高性能应用中。采用固相反应法制备了一系列氮硅酸盐发光材料M2-xSi 5 N8：Eu-x（M = Sr，Ba）。在空气中，只有x = 0.10的Sr_（2-x）Si_（5 N）_8：Eu_x样品发生了热降解，而x = 0.02的Sr_（2-x）Si_（5 N）_8：Eu_x和x = 0.10的Ba类似物样品没有发生热降解。这是一个前所未有的调查研究这一现象在稳定的氮化物。利用原位XRD测量对这些化合物在热处理后的晶体结构变化进行了研究。通过电子能谱（ESCA）和X射线吸收近边结构（XANES）谱确定了化合物中Eu离子的价态。通过透射电子显微镜（TEM）检查这些材料的形态。综合所有结果，可以得出结论，在Sr 2-xSi 5 N8：Eu-x（x = 0.10）中的热降解的起源是由于在氧化加热处理期间在氮化物磷光体颗粒的表面上形成非晶层，这导致Eu离子从二价氧化为三价。这项研究提供了一个新的视角的影响的降解问题的结果，在发光材料的加热过程。
The orange-red emitting phosphors based on M2Si5N8:Eu (M = Sr, Ba) are widely utilized in white light-emitting diodes (WLEDs) because of their improvement of the color rendering index (CRI), which is brilliant for warm white light emission. Nitride-based phosphors are adopted in high-performance applications because of their excellent thermal and chemical stabilities. A series of nitridosilicate phosphor compounds, M2-xSi5N8:Eu-x (M = Sr, Ba), were prepared by solid-state reaction. The thermal degradation in air was only observed in Sr2-xSi5N8:Eu-x with x = 0.10, but it did not appear in Sr2-xSi5N8:Eu-x with x = 0.02 and Ba analogue with x = 0.10. This is an unprecedented investigation to study this phenomenon in the stable nitrides. The crystal structural variation upon heating treatment of these compounds was carried out using the in situ XRD measurements. The valence of Eu ions in these compounds was determined by electron spectroscopy for chemical analysis (ESCA) and X-ray absorption near-edge structure (XANES) spectroscopy. The morphology of these materials was examined by transmission electron microscopy (TEM). Combining all results, it is concluded that the origin of the thermal degradation in Sr2-xSi5N8:Eu-x with x = 0.10 is due to the formation of an amorphous layer on the surface of the nitride phosphor grain during oxidative heating treatment, which results in the oxidation of Eu ions from divalent to trivalent. This study provides a new perspective for the impact of the degradation problem as a consequence of heating processes in luminescent materials.