Excellent red emission via violet-blue excited in aluminate-based phosphors for white LED application
Three types of CaAl 2 O 4 :Li + phosphors singly doped with Eu 3+ , Sm 3+ , and Ho 3+ ions were synthesized using high temperature solid-state reaction method, and the effects of rare-earth ions and doping concentration on the crystal structure, thermal stability and luminescence properties were systematically studied. The XRD patterns show that all Ca 1 − x Al 2 O 4 :0.01Li + , x Re 3+ (Re = Eu, Sm, Ho) phosphors are pure monoclinic CaAl 2 O 4 phase. And these phosphors can be effectively excited by the characteristic excitation wavelength of the corresponding rare earth ions. Notably, when the doping concentration is less than 15 mol%, the corresponding luminous intensity increases monotonically with the increase of Ho 3+ , while the optimal doping amounts for Eu 3+ and Sm 3+ are 9 mol% and 1 mol%, respectively. Additionally, comparative analysis revealed superior energy transfer efficiency from the matrix to the luminescent center in the CaAl 2 O 4 :0.01Li + , Eu 3+ relative to Sm 3+ and Ho 3+ counterparts. More importantly, the Ca 0.91 Al 2 O 4 :0.01Li + , 0.09Eu 3+ phosphors also exhibit excellent thermal and ageing stability. Its luminous intensity exhibited minimal deviation (< 16%) across an extended temperature range (208 ~ 448 K). Furthermore, after 320 h of thermal aging at 100 °C, the sample retained over 98% of its initial fluorescence intensity. This study provides theoretical and experimental basis for the development of CaAl 2 O 4 -based phosphors for solid-state lighting devices.
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