Blue photoluminescence behavior in TmxY1-xAl3(BO3)4 nanopowders and structural correlations

TmxY1-xAl3(BO3)(4) nanocrystalline powders, with x = 0.040, 0.080, 0.120, 0.160, 0.320 and 1.000 in mol, prepared by the polymeric precursor method and heat-treated at 1150 degrees C were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) techniques showing nanoparticles with good crystallinity of rhombohedral phase. Diffuse reflectance spectroscopy was used to determine the bandgap energy values, by using Kubelka-Munk equation, for all samples having values changing between 4.002 and 4.046 eV. Raman spectra were used to investigate the substitution of Y3+ by Tm3+ ions and a significant change was observed for sample with x = 1.000 (TmAl3(BO3)(4)). Also, the photoluminescence (PL) spectra were measured and analyzed, and the emission intensity as a function of x values was evaluated, An emission energy diagram mechanism was also proposed. The PL decay behavior was studied under excitation at 357.5 nm by a pulsed Xe lamp monitoring four Tm3+ emission bands, and upon excitation at 370 nm by a pulsed NanoLED revealing two lifetime components: a fast component (216-131 ns), and a long component (3.25-1.95 mu s). TmxY1-xAl3(BO3)(4) materials presented good structural properties and high emission intensity in the blue region (narrow lines at 451.5 nm and 454.5 nm), especially that with x = 0.080 (8 mol%) having an internal quantum yield of 13%. A blue high emission purity due to Tm3+ D-1(2) -> F-3(4) transition into stable crystalline phase can be applied in lighting devices.