Photoluminescence properties of red emitting Ba₃Bi₂(PO₄)₄:Eu³⁺ phosphor for WLEDs applications

The Eu³⁺ activated Ba₃Bi₂(PO₄)₄ red emitting phosphors were prepared by the conventional solid state reaction method. The phase identification of the phosphors was characterized by using the powder X-ray diffraction (PXRD) patterns. The high resolution scanning electron microscopy (HRSEM) and the photoluminescence properties of Ba₃Bi₂(PO₄)₄:Eu³⁺ phosphors were investigated. Exciting the phosphor at 395 nm (⁷F₀ → ⁵L₆) or 466 nm (⁷F₀ → ⁵D₂) yielded emission bands at 579, 592, 611, 651 and 698 nm, attributed to the various transitions (⁵D₀ → ⁷F_J (J = 0,1, 2, 3, and 4)) of the Eu³⁺ ions in the same order. The dominant emission band at 611 nm was the well known hypersensitive red emission (⁵D₀ → ⁷F₂). The excitation spectrum for the 611 nm emission of the optimized phosphor (for which the maximum luminescence was observed) exhibited several bands peaking at 363, 384, 395, 417 and 466 nm. The observed excitation and the emission spectra could be attributed to the characteristic intraconfigurational 4f–4f transitions of Eu³⁺ ions. The Judd-Ofelt (J-O) intensity parameters (Ω₂ and Ω₄) were determined from the emission spectra of Eu³⁺ ions. The luminescence lifetime measurments were made. The temperature dependent luminescence spectra of Ba₃Bi₂(PO₄)₄:Eu³⁺ under the excitation of 395 nm were studied. The luminescence quantum efficiency was calculated. In addition, the Commission International del'Eclairagethe (CIE) chromaticity coordinates of Ba₃Bi₂(PO₄)₄:Eu³⁺ phosphor was found to be located in the red region (0.6381,0.3615) when excited at 395 nm. From these results it was noted that the Eu³⁺ activated Ba₃Bi₂(PO₄)₄ phosphor could be used as a red emitting phosphor for the near-UV excited WLEDs.