Synthesis and characterization of a Eu<sup>3+</sup>‐activated Ba<sub>2–x</sub>V<sub>2</sub>O<sub>7</sub>:xEu<sup>3+</sup> phosphor using a hydrothermal method: a potential material for near‐UV‐WLED applications
N. Venkatesh Bharathi, T. Jeyakumaran, S. Ramaswamy, S. S. Jayabalakrishnan
Abstract
Abstract Eu 3+ ‐activated Ba 2 V 2 O 7 (Ba 2–x V 2 O 7 :xEu 3+ ) phosphor materials were synthesized using a hydrothermal method and different concentrations of europium (x = 0.01, 0.02, 0.03, 0.04, and 0.05%). Phase purity, structural, morphological, optical, and luminescence characteristics of the as‐synthesized phosphors were studied using powder X‐ray diffraction (XRD), high resolution scanning electron microscopy, UV–visible spectroscopy, and fluorescence spectrometry. The recorded XRD patterns of the as‐synthesized phosphors were indexed and predicted to be a triclinic structure. A cube‐like morphology was obtained for the as‐prepared samples. Broad absorption in the UV region from 200 nm to 380 nm was observed and the good transparency in the visible region at 400–800 nm originated from the [VO 4 ] 3− group charge transfer (CT) transition. The broad emission peak centred at 499 nm was due to the CT band of the [VO 4 ] 3− group. Also, a sharp peak observed at 613 nm was due to the electric dipole transition of 5 D 0 → 7 F 2 of Eu 3+ ions that occupied the lattice sites without inversion symmetry for all concentrations. The colour qualities of the as‐prepared samples were calculated using Commission International de l'Eclairage coordinates. The colour‐rending index (CRI) value was 86 for the Ba 1.97 V 2 O 7 :0.03Eu 3+ phosphor. Furthermore, a WLED with a high CRI value of 95 was achieved by coupling the 3 W 356 nm near‐UV light‐emitting diode (LED) chip with the Ba 2–x V 2 O 7 :xEu 3+ phosphor. These results suggested that the as‐prepared phosphor materials are potential candidates for fabrication of near‐UV chip excited WLEDs.