Ce3+ and Eu3+ emissions in YAG via a core-shell strategy for warm white LED lighting
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YAG:Ce and YAG:Eu sols were synthesized by a polymeric sol-gel route. The crystallization temperature of YAG was determined by X-ray diffraction as a function of the calcination temperature, revealing that YAG starts to crystallize directly from the amorphous phase at 800 °C. The effects of the thermal treatment and the dopant amount on the photoluminescent properties were studied, observing the highest emission after calcination at 1000 °C for 1 h in both cases and with a concentration of 1 and 3 mol% of Ce and Eu, respectively. Core-shell materials were prepared by dipping YAG:Ce or YAG:Eu sintered pellets into the synthesized sols and then, these materials were calcined at 1000 °C for 1 h. An effective energy transfer from Ce to Eu was observed in the sample YAG:Eu (core)–YAG:Ce (shell) when blue light (λ = 465 nm) is used as excitation source. This wavelength excites the Ce but not the Eu; however, in the photoluminescence emission spectrum, the bands associated to both ions can be clearly detected, confirming that the core-shell strategy is a good method for the preparation of warmer white LEDs.
KeywordsYttrium aluminum garnet Cerium Europium Photoluminescence
We acknowledge the funding provided by the Swiss National Science Foundation under project no. IZRPZO_164736/1. This work is a part of the 382-PiGnano project of ERA.Net RUS Plus 2013-2018 initiative under Consortium Agreement with ITMO University (Russia), Swiss Federal Laboratories for Materials Science and Technology (Switzerland), and Hamburg University of Technology (Germany).
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Conflict of interest
The authors declare that they have no conflict of interest.