Photoluminescence properties of red emitting BaGdB9O16: Eu phosphor

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An investigation is reported of the photoluminescence properties of the BaGdB9O16:Eu phosphors. Under VUV excitation, BaGdB9O16:Eu exhibited a bright red luminescence with CIE chromaticity coordinates of (0.66, 0.34). The brightness was 80% of the commercial (Y,Gd)BO3:Eu under identical excitation conditions. The PL spectrum showed a low field splitting of the 7FJ levels of Eu, indicating the Eu ions experience local distortion. It also showed a vibrational mode associated with the Eu-O vibration. The physical mechanism responsible for Eu excitation was investigated by PLE and time-resolved spectroscopy. The PLE spectrum showed sharp lines due to the 8S7/26IJ and 6PJ transitions of Gd3+ in addition to the f-f transitions of Eu3+. The charge transfer band of Eu was observed at 233 nm and the host absorption band was detected at 159 nm. The time-resolved spectroscopy showed that the Eu ions decay purely exponentially with a lifetime of 2.1 ms. Under excitation into the Gd 6IJ level located below the fundamental absorption edge, the Eu luminescence was excited through the energy transfer process from Gd to Eu. The energy transfer rate was estimated to be 6000 s−1.

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