Efficient red‐emitting phosphor of Eu³⁺‐activated (Na_0.5Gd_1.5)(TiSb)O₇ derived via cation‐substitutions in Gd‐Pyrochlore

Abstract

Rare‐earth (RE) titanate pyrochlore with perovskite‐layered structure is a well‐known engineering material in applied in many field. In this work, a red‐emitting phosphor of Gd2−xNaxTi2−2xSb2xO7:Eu3+ (x = 0‐0.5) was developed via cation substitutions of (Sb5+→Ti4+) and (Na+→Gd3+) in Gd2Ti2O7. The motivation is based on the fact that the introduction of cation‐disorders has been regarded to be an effective approach for improving the luminescent efficiency and thermal stability of RE‐activated materials. All the samples were synthesized via facile solid‐state reaction method. The morphology properties were measured via SEM and EDS measurements. The structural Rietveld refinement was performed to investigate the microstructure in pyrochlore lattices. The luminescence properties of Gd2−xNaxTi2−2xSb2xO7:0.15Eu3+ (x = 0‐0.5) has a strict dependence on the cation substitution levels. The band energy of Gd2Ti2O7 is 2.9 eV with a direct transition nature. The incorporation of Sb5+ and Na+ in the lattices moves the optical absorption to a longer wavelength. The cation disorder results in significant improvements of luminescence intensity, excitation efficiency in the blue region, longer emission lifetime and thermal stability.

Eu3+-Activated NaGdF4 Nanorods for Near-Ultraviolet Light-Triggered Indoor Illumination

“…Most of the phosphors were realized by introducing the rare-earth ions into the inorganic hosts, with the resulting colorful emissions being attributed to the 4f–5d and 4f–4f transitions. As a member of lanthanide ions, Eu 3+ ion, which is able to emit an intense narrow red emission at 616 nm triggered by the 5 D 0 → 7 F 2 transition within its intra4f configuration, is thought of a good red-emitting activator. , To date, researchers have demonstrated that the Eu 3+ -ion-based luminescent materials were able to be efficiently pumped by NUV chip and exhibited potential feasibility in white LED applications. − From previous literature, it is obvious that the luminescent performance of the rare-earth ions is greatly affected by the host’s phonon energy. , Specially, when the phonon energy is low, the rate of nonradiative transition can be hindered and the possibility of the radiative transition would be promoted, resulting in high luminous efficiency. Consequently, selecting a suitable host is a feasible technique to modify the luminescent behaviors of the rare-earth ions.…”

Synthesis, structure, and luminescence of Eu3+‐activated La4Ti3O12nanoparticles with layered perovskite structure

“…This effect may result in different changes in crystal symmetry, electric structures, and crystal field strength, which can have great influences on the energy splitting and electronic transition in RE‐activator‐containing perovskites. There have been considerable efforts on investigations of luminescence in RE‐(eg, Eu 3+ , Er 3+ , Pr 3+ , Ce 3+ , and Yb 3+ ) activated perovskite oxides …”

“…Eu 3+ is an activator based on its specialties, ie, its emission lines are very simple compared with the other RE ions. Eu 3+ ions substituted for host cations in a host usually exhibit a bright red emission and it can be easily excited by UV‐ and near UV‐radiation which is strongly absorbed by the charge‐transfer (CT) transition of Eu 3+ …”