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In this work we studied the structural and optical properties of lithium tantalate ͑LiTaO 3 ͒ powders doped with Eu 3+ 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 Eu 3+ luminescence. A direct relation was established between the lattice parameters and the "occupation fraction" of Eu 3+ in each LiTaO 3 site. The occupation fraction was set as the relative population of Eu 3+ ions for each site obtained by means of the intensity, baricenter, and the spontaneous emission coefficients of the 5 D 0 → 7 F 0 transitions. We concluded that the unit cell parameter a presents the same behavior of the Eu 3+ occupation fraction in Ta 5+ sites as a function of the Eu 3+ content in LiTaO 3 . The same was observed for the variation in Eu 3+ occupation fraction in the Li + site and the unit cell parameter c with the Eu 3+ content.

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