Enhanced Red Emission from Bi3+ Sensitized Eu3+ Activated BaLaGa3O7 Phosphors for Solid-State Lighting Applications.

Abstract

Bi³⁺ ions sensitized BaLa_0.95Ga₃O₇:0.05Eu³⁺ ceramic phosphors have been synthesized by the conventional solid state reaction method. The structural, optical and luminescence studies have been investigated. The structural studies include X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy dispersive x-ray spectroscopy (EDAX) via elemental color mapping. The optical and luminescence studies have been performed using UV-Visible absorption spectroscopy (UV-Vis), photoluminescence (PL), temperature dependent photoluminescence (TDPL) and mechanoluminescence (ML) studies. The XRD analysis shows that synthesized phosphors are single phase with a tetragonal structure. There is no significant change in the phase and structure of the host after the introduction of Eu³⁺ and Bi³⁺ ions. The emission spectra excited at 394 nm have been investigated for these wide band gap phosphors (~ 4.75 eV). The phosphors have intense red emission with high color purity and their chromaticity coordinates are very close to the standard red component (0.670, 0.330). The optimized BaLaGa₃O₇:0.05Eu³⁺,0.04 Bi³⁺ phosphor shows excellent thermal stability and retains 91% of its initial intensity at 423 K with activation energy 0.24 eV. Phosphors show good mechanoluminescence (ML) emission without any irradiation of UV or gamma rays. The dependence of ML glow curve intensity on dopant concentration, impact height and impact velocity has been performed. The ML and PL studies reveal that the synthesized phosphors can be potential candidates for stress sensors, UV or near UV LED and phosphor converted WLED applications.