Stable Tunable Luminescence of Hetero-valent Eu Ion Activated Ba₂InTaO₆ Phosphors Synthesized by Defect-Induced Self-Reduction in the Molten-Salt Method

Abstract

Functional materials with stable and adjustable luminescence have recently become a research hotspot for their broad application prospects. Tunable luminescence can be realized by the doping of hetero-valent europium ions. High-temperature hydrogen atmosphere reduction is required in the traditional preparation of Eu 2+ -doped phosphors. Herein, an anoxic molten-salt medium environment was established to form oxygen vacancy defects in the reaction system and induce the self-reduction of Eu 3+ ions to obtain Eu 2+ ions. X-ray photoelectron spectroscopy (XPS) results confirm the existence of Eu 2+ and Eu 3+ ions in the samples, and the fluorescence spectrum shows that hetero-valent Eu ions can synergistically emit light effectively. Under 266 nm ultraviolet light excitation, the white light emission was successfully realized for a Ba 2 InTaO 6 :Eu phosphor by different emission combinations of Eu 3+ and Eu 2+ ions. In addition, the Ba 2 InTaO 6 :Eu phosphor exhibits adjustable luminescence from greenish-yellow to red exciting at 390−490 nm, which has superior stability in a high-temperature and high-humidity environment. Therefore, it is very promising that Ba 2 InTaO 6 :Eu will be used as multi-color functional materials in many fields such as communication encryption and colorful decoration.

Valence regulation in europium-doped fluoride phosphor for high-resolution X-ray time-lapse imaging

“…S4, ESI †), while the Eu 2+ enhances greatly after X-ray irradiation, as depicted in Fig. 5c, 31 which strongly proves the reduction from Eu 3+ to Eu 2+ caused by X-ray. Besides, the XPS of Eu in the original phosphor indicates the self-reduction of Eu 2+ during the high-temperature solid-state reaction.…”

Engineering 3d–2p–4f Gradient Orbital Coupling to Enhance Electrocatalytic Oxygen Reduction

“…For Eu 3d spectrum, the main peaks at the binding energies of 1134.6 and 1164.5 eV are attributed to the Eu 3d 5/2 and Eu 3d 3/2 respectively, corresponding to trivalent Eu 3+ states, while the satellite peaks at the binding energies of 1126.3 and 1156.2 eV are attributed to Eu 2+ states. [ 43,44 ] This oxidation shift between Eu 3+ and Eu 2+ in Eu 2 O 3 is also confirmed by the existence of the multiplet peak at a binding energy of 1142.6 eV. [ 43 ] High‐resolution Eu 4d spectrum is also fitted with two main peaks at 136.29 (4d 5/2 ) and 142.0 eV (4d 3/2 ).…”

Vacancy-Enhanced Self-Reduction of Eu in Pyrophosphate Phosphor

“…defects, each carrying a single positive charge, V Ba ′′ can release free electrons. Meanwhile, due to lattice vibrations, some oxygen atoms escape from their BaO 8 /BaO 9 44,45 Lattice defects are closely related to the selfreduction of RE ions in air. Eu doping generates trap energy levels, which provide an additional electron for adjacent activators to move to lower valence states.…”