After-glow, luminescent thermal quenching, and energy band structure of Ce-doped yttrium aluminum-gallium garnets

Wang

et al. 2021

J Am Ceram Soc.

The exploration of the high thermal stability near‐infrared (NIR) phosphors is significantly crucial for the development of plant lighting. However, NIR phosphors suffer from the poor chemical and thermal stability, which severely limits their long‐term operation. Here, the successful improvement of luminous intensity (149.5%) and thermal stability at 423 K of Zn3Ga2GeO8 (ZGGO): Cr3+ phosphors is achieved for the introduction of Al3+ ions into the host. The release of carriers in deep traps inhibits the emission loss for the thermal disturbance. Furthermore, an NIR light emitting diodes (LEDs) lamp is explored by combining the optimized Zn3Ga1.1675Al0.8GeO8: 0.0325Cr3+ phosphors with a commercial 460 nm blue chip, and the emission band can match well with the absorption bands of photosynthetic pigments and the phytochrome (PR and PFR) of plants. The explored LEDs lamp further determines the growth and the pheromone content of the involved plants for the participation of the NIR emission originated from Cr3+ ions. Our work provides a promising NIR lamp as plant light with improved thermal stability for long‐term operation.

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Improved thermal stability of the near‐infrared Al‐modulated Zn₃Ga₂GeO₈: Cr³⁺ phosphors for plant growth applications

Wang

et al. 2021

J Am Ceram Soc.

“…As seen, a large ε cfs was mainly obtained when Ce 3+ was accommodated in these sites with six or eightfold coordination (which are relatively small coordination numbers) . Among them, the garnet‐type ones have been the dominant commercial green‐to‐yellow phosphors for a long time due to the high quantum efficiency and high thermal quenching temperature . The CaSc 2 O 4 ‐type and Ba 3 Sc 4 O 9 ‐type ones are costly; but uniquely, the Ba 3 Sc 4 O 9 ‐type ones emit orange‐to‐red.…”

Section: Introductionmentioning

confidence: 94%

Local coordination, electronic structure, and thermal quenching of Ce³⁺ in isostructural Sr₂GdAlO₅ and Sr₃AlO₄F phosphors

Asami

et al. 2018

J Am Ceram Soc

Sr2GdAlO5:Ce and Sr3AlO4F:Ce are isostructural phosphors in which the Ce3+ 4f‐5d1 transition can be efficiently excited by a photon with energy lower than 3.1 eV. Herein, we analyze the crystal chemistry of the Ce3+ local coordination, compare the thermal quenching behavior and construct the electronic structure of Ce3+ in them. The Rietveld refinement on two occupancy models suggests that Gd3+ only occupies the 8h site in Sr2GdAlO5; this provides a hint on the preferred occupancy of dopant Ce3+ in this site. The large crystal filed splitting of Ce8h is mainly due to the fact that the 8h site is bonded to two oxygen with relatively short dSr/Gd‐O and forms a quasi‐square antiprism which experiences a large distortion. The Ce3+ 5d‐4f luminescence in Sr3AlO4F is much more stable against thermal quenching than that in Sr2GdAlO5, as evidenced by the temperature‐dependent luminescence intensity and luminescence decay studies. The energy of the O2−‐Eu3+/2+ and O2−‐Ce4+/3+ charge transfer as well as bandgap were estimated and the electronic structure of Ce3+ were constructed. A larger energy barrier ΔEdC between the Ce3+ 5d1 level and the conduction band bottom in Sr3AlO4F is seen from the Vacuum Referred Binding Energy (VRBE) diagrams which explains the higher thermal quenching temperature by thermal ionization model.

“…(Gd,Y,Lu) 3 (Al,Ga) 5 O 12 :Ce 3+ garnets have drawn much attention due to their excellent luminescence as scintillators for CT, , phosphors, or persistent phosphors for WLEDs − and bioimaging . These garnets have tunable luminescence by modifying crystal-field splitting (CFS) .…”

Section: Introductionmentioning

confidence: 99%

Warm White Light with a High Color-Rendering Index from a Single Gd₃Al₄GaO₁₂:Ce³⁺ Transparent Ceramic for High-Power LEDs and LDs

Sun

ACS Appl. Mater. Interfaces

et al. 2018

146

Transparent ceramics (TCs) are promising for high-power (hp) white light-emitting diode (WLED) and laser diode (LD) lighting. However, comfortable warm white light has not been achieved only using a single TC in hp-WLEDs/ LDs. Herein, highly transparent Gd 3 Al 4 GaO 12 :Ce 3+ (GAGG:Ce 3+ ) TCs (transmittance, T = 55.9−80.2%) were prepared via a solid-state reaction. Ce 3+ as a doped activator center in grains plays a positive role in luminescence based on the microstructural investigations by scanning electron microscopy and the cathodoluminescence system. T decreases upon increasing the Ce 3+ concentration and/or the ceramic thickness, whereas the luminous efficacy of hp-WLEDs/LDs goes up. For blue hp-LEDs driven at 350 mA or LDs of 2 W, warm white light with a low correlated-color temperature of ∼3000 K was achieved by a single GAGG:Ce 3+ TC, benefiting from its broad emission band (full width at half maximum, FWHM = 133−137 nm) and abundant red components (peaking at about 568−574 nm). The color-rendering index of hp-WLEDs reaches 78.9. These results are much better than the performance of the traditional Y 3 Al 5 O 12 :Ce 3+ (YAG:Ce 3+ ) TC, indicating that GAGG:Ce 3+ TCs are promising color converters for hp-WLEDs/LDs with a comfortable warm white light. KEYWORDS: Gd 3 Al 4 GaO 12 :Ce 3+ , transparent ceramic, high-power white LEDs, laser-driven lighting, warm white light