Inorganic remote glass film based on yellowish-green (Y, Ba)3(Al, Si)5O12:Ce garnet phosphor for warm white LEDs
Compared with other fluorescent crystal phases, garnet has better structural stability in a glass matrix and renders precisely controllable emissions due to the abundant lattice control positions. In this work, we regulate the coordination field of Ce 3+ ion based on the co-substitution method and achieve the spectra regulation in the yellow–green range. We used Ba 2+ –Si 4+ cations to replace Y 3+ –Al 3+ cations in Y 3 Al 5 O 12 (YAG) matrix to obtain blue-shift of the emission peak from 552 to 539 nm. The centroid shift and crystal field splitting decrease with the decreasing covalency of the bond between the Ce 3+ ion and the surrounding anions owing to the higher electronegativity of Si 4+ ions than Al 3+ ions. The corresponding fluorescent films were prepared by a low-temperature co-sintering process based on the as-made Ba 2+ –Si 4+ co-substituted phosphor. X-ray powder diffractometer and scanning electron microscopy images showed that the fluorescence crystals were less eroded and evenly dispersed in the glass matrix. Spectral analysis showed that the garnet phase was protected by using lead-free borosilicate glass with a low melting point, and the quantum efficiency of phosphor-in-glass (PiG) retains 98% of the corresponding phosphor. By adjusting the ratio of garnet phosphor to commercial red nitride phosphors, a warm white fluorescence with a color rendering index of 80.3 and color temperature of 3899 K was obtained. The prepared warm white film has potential application value in the whole spectra field.
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