Spectral studies of Eu3+-activated Na2Zn5Mo6O24: A novel red-emitting nanophosphor with high quantum efficiency and thermal stability

This study investigates the development of a novel red-emitting nanophosphor, Eu³⁺-doped Na₂Zn₅Mo₆O₂₄, synthesized via a sol-gel method for optoelectronic applications. Eu³⁺ ions, known for the red luminescence via ⁵D₀ → ⁷F₂ hypersensitive transition (∼615 nm), face intrinsic limitations due to weak oscillation absorption in the UV to blue spectral range. To solve this problem, the effective excitation of Eu³⁺ ions in the near-ultraviolet wavelength range was achieved by using the molybdate host Na₂Zn₅Mo₆O₂₄. Structural analysis confirmed a triclinic phase (space group P-1) with phase purity across doping concentrations (x = 0.01–0.06). The nanophosphor exhibited intense red emission (CIE: 0.65, 0.34) under 395 nm excitation, with a quantum efficiency (QE) of 68.5 % and superior thermal stability (activation energy ΔE = 0.279 eV). Optimal performance was observed at x = 0.05, balancing radiative efficiency and concentration quenching. Prototype LEDs integrating the nanophosphor demonstrated high color purity, and a warm-white LED achieved a color rendering index (CRI) of 90, validating its potential for solid-state lighting.