Yttrium tantalate containing high concentrations of Eu3+ as dopant: Synthesis and structural and luminescence features

This study reports the synthesis and the structural and spectroscopic characterization of Eu3+-doped yttrium tantalate prepared by a new sol-gel method, which affords the orthorhombic Y3TaO7 and monoclinic YTaO4. Eu3+ doping influences the crystallization kinetics; its presence delays YTaO4 formation. Spectroscopic studies and their correlation to the structural features were the basis to understand the high quantum efficiency and no evidence of concentration quenching and clustering formation of Eu3+ ions. Inhomogeneous broadening in the emission spectra is due to Eu3+ distribution in different Y3TaO7 symmetry sites. Higher YTaO4 content increases the ratio between the D-5(0)-> F-7(2) and D-5(0)-> F-7(1) transition intensities, suggesting that Eu3+ occupies relatively lower symmetry sites as compared to Eu3+ distribution in the Y3TaO7 phase. No quenching occurs even for samples containing the largest Eu3+ concentration (up to 5.0 mol%), which strongly indicates high Eu3+ solubility within the yttrium tantalate host and absence of Eu3+ clusters. In addition to its application as structural probe, high quantum efficiency values combined with enhanced emission intensity make Eu3+-doped yttrium tantalate a suitable red luminophore.