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

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.