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

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 Eu2+-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 Eu3+ ions to obtain Eu2+ ions. X-ray photoelectron spectroscopy (XPS) results confirm the existence of Eu2+ and Eu3+ 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 Ba2InTaO6:Eu phosphor by different emission combinations of Eu3+ and Eu2+ ions. In addition, the Ba2InTaO6: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 Ba2InTaO6:Eu will be used as multi-color functional materials in many fields such as communication encryption and colorful decoration.