13–16 Obviously, the red-emitting phosphor is an indispensable component for the generation of high-quality white light. 11,12 To circumvent these shortages, another feasible approach was developed, that is, using the ultraviolet (UV) or near-UV (NUV) LED chip to pump the blending tricolor (blue, green and red) phosphors to produce the warm white light. Unfortunately, due to the deficiency of red emission band in the luminescent spectrum, the white light usually suffers high correlated color temperature (CCT) and low color rendering index (CRI). 10 At present, the combination of a blue LED chip and yellow-emitting YAG:Ce 3+ phosphors is a commercially available strategy to generate white light. 1–9 In particular, with the growing awareness of environmental problems and energy consumption, the investigation of phosphor-converted WLEDs is increasing since their utilization can save around 50% of the energy for lighting and they are eco-friendly compared to conventional bulbs. Introduction Over the last few years, considerable efforts have been dedicated to the development of rare-earth (RE) ion-based luminescent materials because of their extensive practicability in various fields, including solar cells, optical bioimaging, noninvasive temperature sensors, latent fingerprinting, white light-emitting diodes (WLEDs) and solid-state lasers. The results suggest that the Eu 3+-activated Gd 2MoO 6 compounds are a promising red-emitting phosphor for WLEDs. Finally, by integrating the resultant compounds with a blue light-emitting diode (LED) chip and yellow-emitting YAG:Ce 3+ phosphors, a white light-emitting diode (WLED) device was fabricated which possessed a correlated color temperature of 5981 K, a color rendering index of 71.76 and a color coordinate of (0.321, 0.378). Additionally, the Judd–Ofelt theory was employed to investigate the local crystal environment around the Eu 3+ ions in the Eu 3+-activated Gd 2MoO 6 phosphors. Furthermore, the temperature-dependent PL emission spectra were recorded to test the thermal stability of the as-synthesized phosphors. The critical distance was around 11.47 Å and the mechanism for the concentration quenching was dominated by dipole–dipole interaction. Meanwhile, the PL emission intensity was strongly dependent on the Eu 3+ ion concentration and the optimal doping concentration for the Eu 3+ ions in the Gd 2MoO 6 host lattice was determined to be around 15 mol%. Upon 360 and 463 nm excitation, bright emissions corresponding to the 5D 0 → 7F J ( J = 0, 1, 2, 3 and 4) transitions of Eu 3+ ions were detected. The photoluminescence (PL) excitation spectra revealed that the obtained phosphors can be efficiently pumped by both near-ultraviolet and blue light. A series of Eu 3+-activated Gd 2MoO 6 phosphors were synthesized via a citric acid-assisted sol–gel route.
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