Photoluminescence properties of red emitting BaGdB₉O₁₆:Eu phosphor

Abstract

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 ⁷F_J 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 ⁸S_7/2 − ⁶I_J and ⁶P_J 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 ⁶I_J 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.