Excellent red emission via violet-blue excited in aluminate-based phosphors for white LED application

Abstract

Three types of CaAl₂O₄:Li⁺ phosphors singly doped with Eu³⁺, Sm³⁺, and Ho³⁺ 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 − xAl₂O₄:0.01Li⁺, xRe³⁺ (Re = Eu, Sm, Ho) phosphors are pure monoclinic CaAl₂O₄ 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 Ho³⁺, while the optimal doping amounts for Eu³⁺ and Sm³⁺ are 9 mol% and 1 mol%, respectively. Additionally, comparative analysis revealed superior energy transfer efficiency from the matrix to the luminescent center in the CaAl₂O₄:0.01Li⁺, Eu³⁺ relative to Sm³⁺ and Ho³⁺ counterparts. More importantly, the Ca_0.91Al₂O₄:0.01Li⁺, 0.09Eu³⁺ 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 CaAl₂O₄-based phosphors for solid-state lighting devices.