Development of red phosphor Li8CaLa2Ta2O13:Eu3+ for WLEDs and anti-counterfeiting applications

Abstract

A set of novel red phosphors Li₈CaLa₂Ta₂O₁₃:xEu³⁺ (LCLTO:xEu³⁺) were successfully prepared using a solid-state reaction method. The properties of the prepared samples, including phase purity, elemental composition, and morphology, were systematically investigated using X-ray diffraction, scanning electron microscopy, and diffuse reflectance spectroscopy analyses. The 610 nm maximum emission peak is attributed to the ⁵D₀→⁷F₂ transition of Eu³⁺ ion under 394 nm irradiation. Among all the LCLTO:xEu³⁺ phosphors, LCLTO:0.6Eu³⁺ showed the strongest emission intensity because of the concentration quenching effect of the electric dipole–dipole interaction among the Eu³⁺ ions, which was also demonstrated by the decay curves. Remarkably, the emission intensity of the optimal LCLTO:0.6Eu³⁺ phosphor, which exhibited a high internal quantum efficiency of 49.30% and excellent color purity of 96.79%, was approximately 2.29 times higher than that of commercial Y₂O₃:Eu³⁺ red phosphors. The thermal stability of the LCLTO:0.6Eu³⁺ sample with good color stability was meticulously investigated. The fabricated white-light-emitting diode (WLED) exhibited a superior color-rendering index of R_a = 82 and chromaticity coordinates of (0.3260, 0.3639), suggesting that LCLTO:0.6Eu³⁺ has potential applicability in developing efficient and high-quality WLEDs. Moreover, the prepared LCLTO:0.6Eu³⁺/PDMS composite film demonstrated exceptional flexural resistance and chemical stability, indicating considerable promise for practical anti-counterfeiting applications.