Synthesis and luminescent properties of a new cyan Ca18Li6-3Y (PO4)14:0.1Eu phosphors and PVA-based composite films for multifunctional applications

The development of light-emitting materials capable of efficiently emitting broad-band cyan light is of paramount importance in the quest for full-spectrum white light illumination. In this study, a series of new Ca18Li6-3xYx(PO4)14:0.1Eu phosphors with adjustable luminescent properties were synthesized through a high-temperature solid-phase method, and the investigation encompassed an analysis of their crystal structures, luminescence characteristics, and thermal stability. Meanwhile, the optimal doping concentration of Y3+ ions in the Ca18Li6-3xYx(PO4)14:0.1Eu host was identified to be x = 0.3, achieved through the modulation of the substitution ratio of Y3+ to Ca2+ to regulate the occupancy of Eu2+ at different sites. The resulted in the generation of asymmetric cyan color emission spectra (FWHM = 47 nm) with broad-band emission spanning the 425–550 nm range under 378 nm excitation. In addition, the application of the optimized cyan-emitting phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu in w-LED devices led to a significant enhancement in the CRI from 89.1 to 91.2, accompanied by a reduction in the correlated color temperature from 4896 K to 4566 K. These results highlight the potential utility of the cyan-emitting Ca18Li5.1Y0.3(PO4)14:0.1Eu phosphors in full-visible-spectrum solid-state illumination. Notably, the optimized cyan-emitting phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu was synthesized in conjunction with soluble polyvinyl alcohol (PVA) to yield a transparent anti-counterfeiting ink. The resulting film exhibited exceptional flexibility, foldability, and superior thermal and optical properties. Moreover, the emission band of this phosphor, situated in the 425 nm–550 nm spectral region, represents a crucial blue light source beneficial for plant growth. In summary, the highly efficient phosphor Ca18Li5.1Y0.3(PO4)14:0.1Eu is a promising material with multifunctional luminescent potential for general illumination, anti-counterfeiting, and light-converting agricultural films.