Luminescence and luminescence quenching of efficient GdB₅O₉:Eu³⁺ red phosphors

This work concerns polycrystalline GdB₅O₉:Eu³⁺, which were made as single phase samples by a simple aqueous sol-gel method. The phase formation of the samples was monitored by X-ray diffraction measurements. Excitation of the synthesized phosphors with near-UV radiation resulted in bright red emission with excellent colour saturation. The colour coordinates were relatively stable regardless Eu³⁺ concentration and temperature increase. Furthermore, under 394.5 nm excitation quantum efficiency of the phosphors doped with up to 25% Eu³⁺ is 100%, what is excellent for practical application. The endmember of the series, EuB₅O₉, possessed quantum efficiency of about 64%, which is still high for a compound with such large Eu content. Temperature dependent emission spectra revealed emission intensity decrease upon increasing temperature and that the samples doped with 1%, 50%, and 100% Eu³⁺ lose half of their photoluminescence efficiency at 891, 603, and 515 K, respectively. Besides, the unique emission spectra profile makes these luminescent materials very attractive for application in luminescent security pigments.