Simultaneous enhancement of red emission and densification in spark-plasma-sintered YAG: Ce transparent ceramics via Si3N4 additive

In present work, Ce 3 + -doped Y 3 Al 5 O 12 (YAG: Ce) transparent ceramics were fabricated via spark plasma sintering (SPS) using Si 3 N 4 as a multifunctional sintering additive. The effects of Si 3 N 4 on the microstructure, densification behavior, and luminescent properties were systematically investigated. It is demonstrated that Si 3 N 4 could be effectively incorporated into the YAG lattice through a charge-balanced substitution mechanism in which Si 4+ -N 3- pairs replace Al 3+ -O 2- , resulting in a significant redshift of the Ce 3+ emission from 545 nm to 582 nm due to enhanced crystal field splitting and nephelauxetic effects. Furthermore, the substitution process also yields in-situ formation of SiO 2 , which promotes densification via liquid-phase sintering, achieves a relative density exceeding 99.5 %, and partially mitigates carbon contamination. When applied in phosphor-converted white LEDs, the Si 3 N 4 -doped YAG: Ce ceramics enabled a substantial reduction in correlated color temperature (CCT) from 4903 K to 3196 K, demonstrating their potential as efficient warm-white light converters without requiring additional red phosphors.