Novel blue-emitting phosphors - BaBeSiO₄: Eu²⁺: Luminescence properties and its application for UV-light emitting diodes

A new Eu²⁺-doped barium beryllium silicate, BaBeSiO₄:xEu²⁺ (1% ≤ x ≤ 10%) phosphor was successfully synthesized by the high temperature solid-state reaction. The phosphor system was investigated as a novel candidate for phosphor-converted white light-emitting diode (LED) applications. The evolution of luminescence and structure of the phosphors induced by variation of sintering temperature are investigated using photoluminescence spectra and X-ray diffraction techniques. The concentration quenching and thermal quenching process of the phosphor were also investigated in detail. The BaBeSiO₄:Eu²⁺ phosphor exhibits broad excitation spectra ranging from 250 to 400 nm, and a blue emission band centered at 460 nm under λ_ex = 337 nm. The main parameters of the electron-vibrational interaction, such as Huang-Rhys factor, effective phonon energy, and zero-phonon line position, were all estimated. The optimal concentration of Eu²⁺ ions in BaBeSiO4 was determined to be 3 mol.%. The corresponding concentration quenching mechanism was verified to be the electric dipole-dipole interaction. The activation energy of BaBeSiO₄:Eu²⁺ for thermal quenching was calculated to be 0.19 eV with the Arrhenius equation. The LED device exhibited an excellent color-rendering index Ra of 90.13 at a correlated color temperature of 4077 K with CIE color coordinates of (0.38, 0.39) under a 350 mA forward-bias current. Based on these results, we are currently evaluating the potential application of BaBeSiO₄:Eu²⁺ as a white-emitting UV-convertible phosphor for high power LED applications.