Cold Sintering of Highly Transparent Calcium Fluoride Nanoceramic as a Universal Platform for High-Power Lighting

摘要

A thermally robust all-inorganic color converter is imperative to high-powerlight-emitting diode (LED) lighting. However, it remains challenging to finda universal inorganic matrix for encapsulating multicolor phosphors due tothe hurdle of achieving a highly transparent medium at a moderate temperature.Here, the densification of calcium fluoride (CaF_2) nanoceramic withvisible transmittance up to 75% at merely 350 ℃, benefiting from an acidmediatedcold sintering process of oxygen-segregated CaF_2 nanoparticlesis reported. Using the optically isotropic CaF_2 as a transparent platform, aY_3Al_5O_(12):Ce~(3+) (YAG: Ce) phosphor-based phosphor-in-ceramics (PiC) converterwith luminous efficacy as high as 190 lm W?1 is fabricated. The ultralowtemperature enables the PiC converter to be further combined with red-emittingCaAlSiN_3:Eu~(2+) (CASN:Eu), delivering a color-rendering index of 92. Thecold-sintered CaF_2 nanoceramic demonstrates great potential as a generalsolution for next-generation high-power LED lighting.