Synthesis, optical properties, and applications of Eu3+, Na+-doped high-color-purity Sr3MgNb2O9 red phosphors for w-LEDs and the detection of latent fingerprints

Abstract

A series of novel phosphors, doping Eu3+ and Na+ ions in the Sr3MgNb2O9 (SMNO) crystal lattice (SMNO:xEu3+, xNa+, x = 0.5–30 mol%), was successfully synthesized through high-temperature solid-state reaction. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the successful synthesis of SMNO:Eu3+, Na+. The phosphor belongs to the hexagonal crystal system and the P3¯m1 (No.164) space group. The bandgap energy of SMNO was calculated with Materials Studio and measured with the use of diffuse reflectance spectroscopy. The excitation spectrum of SMNO:Eu3+, Na+ displays multiple narrow absorption peaks in the violet-blue region as well as a charge transfer band (CTB) near 300 nm, exhibiting the highest peak at 394 nm. Four distinct characteristic peaks are observed in the emission spectrum of SMNO:Eu3+, Na+. Notably, the peak at 601 nm shows the highest emission intensity due to the radiative transition from 5D0→7F2. By varying doping concentrations, it was determined that an optimal concentration of 5 mol%Eu3+ resulted in phosphors, with high color purity exceeding 99 %. Concentration quenching is attributed to the nearest neighbor ions interaction. Furthermore, SMNO:Eu3+, Na+ exhibited good stability in 300–480 K, with luminescent intensity remaining 68.6 % at 420 K and 54.4 % at 480 K compared to room temperature (300 K). The internal quantum efficiency (IQE) of SMNO:5%Eu3+, 5 %Na+ is 65.0 %. Both red and white light-emitting diodes (LEDs) were prepared using SMNO:Eu3+, Na+. The chromaticity coordinates of w-LED were measured as (0.357, 0.376), correlating to a correlated color temperature (CCT) of 4685 K and exhibiting a good color rendering index (CRI, Ra = 88). Additionally, the latent fingerprint (LFP) development demonstrated clear visualization of Levels I-III characteristic structures of fingerprints when utilizing SMNO:Eu3+, Na+. These findings suggest promising applications for SMNO:Eu3+, Na+ in w-LED lighting and LFP development.