Green emitting Ba1.5Lu1.5Al3.5Si1.5O12: Ce3+ phosphor with high thermal emission stability for warm WLEDs and FEDs
By hetero-valence substituting Ba 2+ -Si 4+ for Lu 3+ -Al 3+ pair in Lu 3 Al 5 O 12 : Ce 3+ , a new green phosphor Ba 1.5 Lu 1.5 Al 3.5 Si 1.5 O 12 : Ce 3+ (BLAS: Ce 3+ ) has been obtained. It crystallizes in garnet structure with space group Ia -3 d (230). In the structure, Ba 2+ ions are incorporated into both dodecahedral Lu 3+ and octahedral Al 3+ sites while Si 4+ ions only occupy tetrahedral Al 3+ sites. Under the blue light irradiation of 450 nm, an intense green light peaking at 520 nm was observed and the PL spectrum can be fitted in two Gaussian components, due to the crystal field splitting of Ce 3+ 5 d states under D 2 symmetry constrains. The optical doping concentration of BLAS: Ce 3+ is 6% mol, of which the IQE and EQE are 89.1% and 51.8%, respectively. Furthermore, this sample exhibits an extremely good thermal stability, i.e. the integrated emission intensity is still more than 90% of the initial intensity at 480 K. Then, a w-LED device was fabricated from this new green phosphor BLAS: Ce 3+ and commercial red phosphor (Ca,Sr)AlSiN 3 : Eu 2+ , which shows a quite high color rendering (Ra = 88.2) and a relatively low color temperature 4772 K. Besides, the phosphor exhibits a stable chromaticity under different acceleration voltages. The phosphor may be promising material for the development of solid-state lighting and display systems.
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