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High-power white-light-emitting diodes (WLEDs) comprising binderless bulk phosphors and ultraviolet (UV) LED chips as next-generation illumination sources were intensively studied. The main challenge is the effective management of different color components in each suitable crystal phase while maximizing their optical properties with near-UV excitation. In this regard, we developed glass-ceramics that contain Na5Gd9F32 and NaAlSiO4, in which the phase-selective distribution of Eu3+ and Eu2+ results in warm white-light emission with a low correlated color temperature (CCT) (< 3000 K), high color rendering index (Ra > 70), and promising thermal stability. The obtained composite exhibits broadband photoluminescence (PL) around the blue–green (NaAlSiO4:Eu2+) and red (Na5Gd9F32:Eu3+) spectral regions. Up to 573 K, the PL intensity remains above 50% of that at room temperature (RT). The internal PL quantum yield was estimated as 35%. Further, a thermal-aging test was conducted for 1000 h at 573 K, after which the sample exhibited 70.7% of the initial PL intensity at RT and showed stability in the chromaticity coordinate for a warm white range. This study, which exhibits potential for practical applications, provides a strategy for the generation of a warm white-light color with Eu2+ and Eu3+ in oxide and fluoride phases in combination with UV LEDs.

Aluminum (Al) is known as a plasmonic material effective in a wide frequency range up to the ultraviolet, while its plasmonic properties in the near infrared region have been less explored. In this study, up‐conversion (UC) photoluminescence is amplified by using an Al nanostructure to demonstrate that Al is a useful plasmonic material in the near infrared region as well. A periodic lattice of Al nanocylinders is selected as a plasmonic nanostructure, where the size of nanocylinder and the period of the lattice are tuned to match both the localized surface plasmon resonance and in‐plane diffraction to the absorption wavelength (λ = 980 nm) for the UC process. Core–shell‐type UC nanoparticles (NPs) are designed to suppress the energy transfer from NPs to Al cylinders which reduces the UC photoluminescence intensity. The resulting optimized core–shell UCNPs combined with the Al plasmonic lattice leads to over 100‐fold enhancement of UC intensity. The use of Al instead of conventional Au as a plasmonic material is beneficial from the point of view of low cost and abundance of element.