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

A thermally robust all-inorganic color converter is imperative to high-power light-emitting diode (LED) lighting. However, it remains challenging to find a universal inorganic matrix for encapsulating multicolor phosphors due to the hurdle of achieving a highly transparent medium at a moderate temperature. Here, the densification of calcium fluoride (CaF2) nanoceramic with visible transmittance up to 75% at merely 350 degrees C, benefiting from an acid-mediated cold sintering process of oxygen-segregated CaF2 nanoparticles is reported. Using the optically isotropic CaF2 as a transparent platform, a Y3Al5O12:Ce3+ (YAG: Ce) phosphor-based phosphor-in-ceramics (PiC) converter with luminous efficacy as high as 190 lm W-1 is fabricated. The ultralow temperature enables the PiC converter to be further combined with red-emitting CaAlSiN3:Eu2+ (CASN:Eu), delivering a color-rendering index of 92. The cold-sintered CaF2 nanoceramic demonstrates great potential as a general solution for next-generation high-power LED lighting.

Automated summary

This article reports a thermally robust all-inorganic color converter that can be used for high-power LED lighting. By utilizing an acid-mediated cold sintering process, oxygen-segregated CaF2 nanoparticles are densified, resulting in a visible transmittance of up to 75% at only 350 degrees C. Using optically isotropic CaF2 as a transparent platform, a phosphor-in-ceramics (PiC) converter based on Y3Al5O12:Ce3+ (YAG: Ce) phosphor is fabricated, achieving a luminous efficacy as high as 190 lm W-1. The cold-sintered CaF2 nanoceramic shows great potential as a general solution for next-generation high-power LED lighting.