Luminescence enhancement and thermal stability of alkali co-doped Eu3+:LaMgB5O10 phosphors

Abstract

Eu3+-activated LaMgB5O10 (LMBO:Eu3+) phosphors were synthesized and systematically investigated to eluci date the role of alkali co-doping (Li+, K+) on their structural and luminescence properties. XRD, Raman, and FTIR analyses confirmed the phase purity and revealed subtle lattice distortions upon alkali incorporation, while SEM/ EDS verified homogeneous dopant distribution. Photoluminescence spectra are dominated by the characteristic 5 D0→7 FJ transitions of Eu3+, with alkali ions inducing pronounced modifications in band distribution and emission intensity. Li+ co-doping yields a moderate enhancement and redistributes oscillator strength toward the 5 D0→7 F4 transition, whereas K+ co-doping produces nearly an order of magnitude increase in far-red emission. Judd–Ofelt analysis provided intensity parameters (Ω2, Ω4, Ω6), radiative lifetimes, and quantum efficiencies, highlighting the impact of alkali-induced site symmetry perturbations. Temperature-dependent PL measurements revealed distinct quenching and anti-thermal quenching (ATQ) behaviors: undoped Eu3+ exhibited conventional quenching with an activation energy of 0.404 eV, K+ co-doping reduced the barrier to 0.205 eV and triggered moderate ATQ above 470 K, while Li+ co-doping produced strong ATQ with emission intensity increasing nearly fourfold at 550 K. These findings demonstrate that alkali co-doping not only enhances far-red emission at room temperature but also stabilizes or even amplifies luminescence at elevated temperatures, making LMBO:Eu3+,M+ phosphors promising candidates for high-power pc-WLEDs and plant-growth lighting.