Correlation between the spectroscopic and structural properties with the occupation of Eu³⁺ sites in powdered Eu³⁺-doped LiTaO₃ prepared by the Pechini method

In this work we studied the structural and optical properties of lithium tantalate (LiTaO₃) powders doped with Eu³⁺ ions. We have examined the different sites occupied by the rare earth ion through the correlation of the DRX data analyzed with the Rietveld method and some spectroscopic parameters derived from the Eu³⁺ luminescence. A direct relation was established between the lattice parameters and the “occupation fraction” of Eu³⁺ in each LiTaO₃ site. The occupation fraction was set as the relative population of Eu³⁺ ions for each site obtained by means of the intensity, baricenter, and the spontaneous emission coefficients of the ⁵D₀→⁷F₀ transitions. We concluded that the unit cell parameter a presents the same behavior of the Eu³⁺ occupation fraction in Ta⁵⁺ sites as a function of the Eu³⁺ content in LiTaO₃. The same was observed for the variation in Eu³⁺ occupation fraction in the Li⁺ site and the unit cell parameter c with the Eu³⁺ content.