A wide-band excited red phosphor GdNb2VO9:Eu3+ with abnormal thermal quenching for latent fingerprints, security ink, and WLEDs

Abstract

The high-temperature solid-state reaction synthesized GdNb2VO9:Eu3+ phosphors. The phase purity, luminescent properties, and thermal stability were systematically studied in this work. By monitoring the emission peak at 619 nm, GdNb2VO9:Eu3+ phosphors present a broad absorption band due to the O2-→Eu3+ and O2-→V5+ charge transfers. Under 306 nm excitation, GdNb2VO9:5 mol%Eu3+ phosphor presents four emission peaks at 593, 619, 651, and 698 nm corresponding to the electron transition from 5D0 to 7F1, 7F2, 7F3, and 7F4, respectively. By the calculation of the Judd-Ofelt parameters (Ω2, Ω4), it is concluded that Eu3+ occupies the non-centrosymmetric lattice in the main lattice. The best doping concentration of GdNb2VO9:xEu3+ is optimized as x = 5 mol%. The chromaticity coordinates of GdNb2VO9:xEu3+ show high color stability and are located in the red region. The GdNb2VO9:Eu3+ phosphors have abnormal thermal quenching behavior and excellent thermal stability. Internal quantum efficiency (IQE) is measured as 62.2 + 0.1%. The latent fingerprints (LFPs) visualized by GdNb2VO9:Eu3+ phosphors display high resolution and high contrast, which easily identify fingerprint level 1–3 characteristics. The security ink made of GdNb2VO9:Eu3+ is successfully used for anti-counterfeit labels and data encryption. Additionally, the prepared white light emitting diode (WLED) has a good color rendering index (Ra = 87) with Commission International de L′ Eclairage (CIE) coordinates (0.343, 0.327). Therefore, GdNb2VO9:Eu3+ phosphors have excellent luminescent properties and broad application prospects.