Combustion derived single phase Y4Al2O9:Tb3+ nanophosphor: crystal chemistry and optical analysis for solid state lighting applications

Abstract

Cool green light emanating monoclinic Y_4−xAl₂O₉:xTb³⁺ (x = 1–5 mol%) nanophosphors have been fabricated through gel-combustion method. X-ray diffraction and transmission electron-microscopy data have been utilized to assess their structural and microstructural characteristics, including cell parameters and crystallite size. Uneven aggregation of nanoparticles in the nano-scale with distinctive porosity can be seen in the TEM micrograph. Kubelka–Munk model imitative diffuse reflectance spectra and an optical band gap of 5.67 eV for the Y_3.97Al₂O₉:0.03Tb³⁺ nanophosphor revealed high optical quality in the samples, which were thought to be non-conducting. The emission (PL) and excitation (PLE) spectra as well as lifetime measurements have been used to determine the luminescence characteristics of the synthesized nanophosphors. The emission spectra show two color i.e. blue color due to ⁵D₃ → ⁷F_J (J = 4 and 5) transitions and green color due to ⁵D₄ → ⁷F_J (J = 3, 4, 5 and 6) transitions. The most dominant transition (⁵D₄ → ⁷F₅) at 548 nm was responsible for the greenish color in focused nanocrystalline samples. Calculated colorimetric characteristics such as CIE, and CCT along with color purity of the synthesized nanocrystalline materials make them the best candidate for the solid-state lighting (SSL).