Structure,Chemical State and Luminescent Properties of Ce,Gd:YAG Transparent Ceramic for Flip-chip White LED Application

Ce,Gd:YAG transparent ceramic was prepared by tape casting and solid state reaction method. Meanwhile, its crystal structure, chemical state and luminous properties were discussed. The prepared samples are identified as pure garnet structure by the XRD results. The valence states of tetravalent and trivalent Ce ions were identified distinctly by X-ray photoelectron spectroscopy. A strong broad band yellow emission was found in photoluminescence(PL) spectra. The quantum yield reached 90.2% at room temperature. When collaborated with a 1.0 mm × 1.0 mm flip-chip, a luminous efficiency(LE) as high as 116.5 lm/W with a correlated color temperature(CCT) of 6627 K at a power dissipation of 1.13 W at 350 m A was demonstrated, indicating that Ce,Gd:YAG transparent ceramics had a promising potential for high power white light-emitting diodes.     

LED的COB封装热仿真设计

通过对COB封装中常用的陶瓷基板和金属基板这两类不同的基板材料进行有限元热仿真模拟,获得各自芯片到基板的仿真热阻,再使用红外热成像仪得到两种基板各自的表面温度分布情况并计算出实际热阻。仿真热阻与实际热阻的一致性表明了所采用的仿真计算方法的可用性。利用有限元仿真对COB封装的热管理方案进行了优化分析。研究表明:相对于金属基板,陶瓷基板由于无绝缘层这一散热瓶颈,其芯片到基板的热阻值约为金属基板封装方案的1/2;而且陶瓷基板有着更大的热管理优化空间,能更好地满足大功率LED封装的散热需要。     

Facile Synthesis,Crystal Structure,and Adsorption Property of Small Titanate Nanowires

Small titanate nanowires with NaTi_2O_4(OH) formulation were directly synthesized via the hydrothermal reaction of amorphous titanate particles with concentrated Na OH solution.The average width of these nanowires is smaller than 20 nm,and the surface area is higher than 200 m~2/g.Compared with the larger nanowires obtained by the hydrothermal treatment of crystalline titania in alkaline solution,these small nanowires exhibit larger adsorption capacities and faster adsorption rate in the removal of both heavy metal ions and dyes.