BaS:Eu,Dy phosphors were prepared by high temperature solid-state method with BaSO 4 as matrix raw material, Eu 2 O 3 and Dy 2 O 3 or Eu 2 (SO 4 ) 3 ·8H 2 O and Dy 2 (SO 4 ) 3 ·8H 2 O as doped ion raw materials. BaSO 4 can be completely reduced after 3 h sintering at 1200 °C in CO atmosphere and pure BaS was obtained in one step. Meanwhile, the rare earth ions were embedded in the host lattices and had no impact on the main structure of the products. However, X-ray diffraction peaks shift shows rare earth doping can cause lattice distortion with the increase of sintering temperature . The luminescence characteristics of BaS:Eu,Dy, BaS:Eu, BaS:Dy and BaS are compared in order to study the luminescence mechanism. It is confirmed that the broad emission locating in the near-infrared (NIR) region should be assigned to 4f 6 5 d 1 →4f 7 transition of Eu 2+ , and the emission locating in the visible region comes from S-related defects in the matrix. Sulfur-rich is particularly detrimental to NIR luminescence. In relatively S-rich systems, there is serious energy transfer between Eu 2+ and S-related defects, which leads to fluorescence quenching. The products are in S-rich state when Eu 2 (SO 4 ) 3 ·8H 2 O and Dy 2 (SO 4 ) 3 ·8H 2 O are selected as raw materials of doped ions. BaS:Eu,Dy inclines to emit visible light with the sintering temperature increasing. By contrast, the products are in Sulfur-deficiency state when Eu 2 O 3 and Dy 2 O 3 are used as raw materials of doped ions and BaS:Eu,Dy only gives NIR emission.
Xingyuan Tao,Xiaoxia Duan,Guang Zheng,Yiwen Liu,Qingxue Zhao,Dawei Wang,Lixin Yi
Core-shell precursor boosts Eu 2+ dispersion and NIR emission in BaS host. • Wet-chemistry-assisted synthesis suppresses S-related defects, enabling NIR emission. • S-related defects act as both luminescent and quenching centers in BaS:Eu. This study develops an innovative wet-chemistry-assisted method for synthesizing BaS:Eu near-infrared (NIR) phosphors. By sequentially precipitating Eu 3+ and Ba 2+ in alkaline solution, a core-shell BaSO 4 @Eu(OH) 3 precursor is obtained, in which the subsequently formed BaSO 4 is inferred to encapsulate the preformed Eu(OH) 3 nuclei. SEM/EDS and XPS analysis show no detectable Eu on the particle surface, supporting this core–shell-like configuration. After sintering in CO reducing atmosphere at 1300 °C, BaS:Eu 2+ is obtained. Under 450 nm excitation, the material exhibits strong NIR broadband emission centered at 715 nm, attributed to the 4 f 6 5d 1 →4 f 7 transition of Eu 2+ in the octahedral crystal field of BaS. Compared with conventional solid-state routes using Eu 2 O 3 or Eu 2 (SO 4 ) 3 , this wet-chemistry-assisted approach appears to improve doping homogeneity in the product system and reduce Eu 2+ aggregation on the particle surface, as reflected in enhanced absorption characteristics and NIR emission intensity. The core-shell precursor configuration is suggested to suppress sulfur-related defect emission by limiting Eu exposure at the particle surface and by controlling the Ba-to-S ratio. Analysis of the luminescence behaviors indicates that sulfur-related defects act as both emission and quenching centers. Overall, this work offers a precursor-engineering strategy that may be extended to develop high-performance NIR-emitting materials. Download: Download high-res image (175KB) Download: Download full-size image
危险品化学品经营许可证（带存储）