Synthesis and Greenish-Yellow Luminescence Properties of Li₆AlGd(BO₃)₄: Tb³⁺ Phosphors for Solid State Lighting

The Li6AlGd(1-x)(BO3)(4):xTb(3+) (0 & LE; x & LE; 4.0 mol%) phosphors are fabricated via solid-state reaction process. The structural investigations are carried out through powder X-ray diffraction and Fourier transform infrared techniques. The morphology is examined using high-resolution scanning electron microscope and transmission electron microscope. The temperature-dependent luminescence properties are completed at 378 nm excitation. The photoluminescence excitation analysis is carried out by controlling the emission at 545 nm corresponding to Tb3+:D-5(4) & RARR; F-7(5) transition. The suitable excitation wavelength is selected as 378 nm for efficient emission by studying the emission spectra at several excitation wavelengths. The emission spectra show two groups of emission bands through Tb3+:D-5(3) & RARR; F-7(J) and Tb3+:D-5(4) & RARR; F-7(J) transitions. The concentration-dependent investigations reveal the optimum Tb(3+)ions concentration as 2.0 mol% for intense luminescence. Upon 378 nm excitation, they produce greenish-yellow luminescence of color purity 60% with CIE color coordinates (0.286, 0.572) close to the standard European Broadcasting Union Green Illuminant and they found suitability in the design of solid-state lighting devices.