Preparation of Transparent Ce³⁺:GdYAG Ceramics Phosphors for White LED

Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

“…One shortcoming is that, for warm-white lighting, YAG:Ce 3+ has low color rendering and high correlated color temperature due to its lack of a sufficient red portion in the emission spectrum. To overcome this, partially replacing the Y 3+ sites with less electronegative La 3+ or Gd 3+ [6, 56] and more recently doping YAG with Si 3 N 4 to form the oxynitride solid solution of Y 2.925 Ce 0.075 Al 5− x Si x O 12− x N x ( x < 0.4 for phase pure garnet) [57] were shown to be able to push down the lowest crystal-splitting component ( 2 D 3/2 ) of the 5d 1 excited level to yield red-shifted emissions. Red-shifting can also be achieved by partially substituting Al 3+ with Mg 2+ –Si 4+ pairs on the octahedral and tetrahedral sites, respectively, to enhance lattice covalency [58, 59].…”

“…YAG:Ho 3+ and YAG:Er 3+ are important infrared (IR) laser materials for medical surgery, since their fluorescence lines (∼2 μ m for Ho 3+ and ∼3 μ m for Er 3+ ) match well with the water absorptions of the human body [5]. Transparent YAG:Ce 3+ ceramic is nowadays being developed as an encapsulant for white-light emitting diodes (LEDs) to replace the widely used but readily degradable resin sealant [6]. Since the parity-law allowed 4f 0 5d 1 → 4f 1 5d 0 transition of Ce 3+ has a very short fluorescence lifetime of ∼10–100 ns and the intrinsic quenching temperature of Ce 3+ in YAG is very high (>700 K) [7], YAG:Ce 3+ transparent ceramic has been considered as a scintillator [8], but does not seem to have a satisfactory stopping power for the incident radiations (x-, α - or γ -rays) owing to the relatively low theoretical density of YAG (∼4.55 g cm −3 ) and the small atomic weight of Y (∼89).…”

Glass‐Ceramics and Solid‐State Lighting

“…This material has good efficiency and excellent heat‐resistance and mechanical strength. Other ceramic phosphor also reported by many researchers in those days . Recently, translucent polycrystalline ceramic phosphor, Eu: CaAlSiN 3, was reported by Tatami et al ., in Annual meeting of The Ceramic Society of Japan (2015, Okayama).…”

Composition and structure design of three-layered composite phosphors for high color rendering chip-on-board light-emitting diode devices

“…or partial substitute of Y 3+ by different ions (Gd 3+ , etc.) in YAG:Ce to add red spectral components in its spectrum, but usually with a sacrifice in luminous efficacy [15][16][17][18][19]. Alternatively, composite phosphor ceramics consisting of both red-and yellow-emitting phosphors are expected to realize high color rendering lighting.…”