No abstract

No abstract

No abstract

The present work reports on the synthesis, structural and optical properties of (Y 1-x Eu x) 4 Al 2 O 9 powders, with x ranging from 0.001 to 0.030. We prepared the materials using a modified polymeric precursors method, and the effect of annealing temperature and Eu 3+ concentrations were evaluated. Structural and microstructural parameters, such as cell parameters, crystallite size and grain size were determined and evaluated by using the results from X-ray diffraction and high-resolution transmission electron microscopy techniques. An annealing temperature of 800°C was enough to obtain single Y 4 Al 2 O 9 crystalline phase with good distribution of Eu 3+ ions. Diffuse reflectance spectra and optical bandgap of 4.52 eV for (Y 0.995 Eu 0.005) 4 Al 2 O 9determined by Kubelka-Munk modelshowed good optical quality of the samples, which were considered non-conducting. All doped samples possessed visible photoluminescence emission from Eu 3+ ions under excitation at 393 nm, with higher emissions occurring in the red region from 5 D 0 → 7 F 2 transition, with R/O relation of 1.69 for the sample with x = 0.010. Analyzing photoluminescence emission spectra, the lifetime values and Judd-Ofelt parameters, we determined that Eu 3+ occupied three different sites of the Y 4 Al 2 O 9 (YAM) structure, replacing Y 3+ ions, with the quenching concentration occurring between x = 0.020 and x = 0.030. We noted that Eu 3+ ions are in a chemical environment with low polarization, and their degree of covalence is low. Finally, samples with x = 0.020 (Y 0.980 Eu 0.020) 4 Al 2 O 9 seems to be useful as red phosphors.