Tunable emission from LiBaBO₃:Eu³⁺;Bi³⁺ phosphor for solid-state lighting

Europium (Eu³⁺) and bismuth (Bi³⁺) co-activated LiBaBO₃ powder phosphors were synthesized by a solid-state reaction and the structure, particle morphology, optical and photoluminescent properties were investigated. X-Ray diffraction patterns of the LiBaBO₃ phosphors crystallized in a pure monoclinic phase, i.e. there were no secondary phases due to either incidental impurities or undecomposed starting materials. Scanning electron microscopy images showed that the powders were made up of fluffy needle-like particles that were randomly aligned. The band-gap of the LiBaBO₃ host was estimated to be 3.33 eV from the UV/vis absorption data. Blue emission was observed from the LiBaBO₃ host, which is ascribed to self-activation of the host matrix. In addition, greenish-blue (493 nm) and red (613 nm) emissions were observed from europium-doped samples and were attributed to the emissions of Eu²⁺ and Eu³⁺, respectively. Furthermore, after codoping with Bi³⁺, the emission intensity of Eu³⁺ located at 613 nm was significantly enhanced. From the Commission Internationale de I′Eclairage (CIE) color coordinates, white emission was observed from LiBa_1–xBO₃:xEu³⁺ (x = 0.020 and 0.025) phosphor powders with color coordinates of x = 0.368, y = 0.378 and x = 0.376, y = 0.366, respectively.