Site selective luminescence spectroscopy of Eu3+ in the rhombohedral pyrochlores Mg2La3Sb3O14 and Ca2La3Sb3O14: Observation of Eu3+ in a strongly distorted site.

Low temperature site selective spectroscopy has been used to probe the distribution of the Eu3+ ion on sites available in the ordered and disordered pyrochlores, Mg 2 La 3 Sb 3 O 14 and Ca 2 La 3 Sb 3 O 14. While the Mg-pyrochlore shows the presence of a single site with inversion symmetry, the emission spectrum of the Ca-pyrochlore is indicative of the presence of several different non-centrosymmetric sites for the dopant ion. These observations are consistent with the structural model that was proposed earlier. The 5D 0 →7F 0 emission transition in the Ca-pyrochlore occurs at very high energy (17,550 cm−1) and under a very specific excitation wavelength. Possible explanation for this observation is provided. • Low temperature site selective luminescence spectra have been measured on Mg 2 La 3 Sb 3 O 14 and Ca 2 La 3 Sb 3 O 14 doped with Eu3+. • A sharp 5D 0.→7F 0 line has been observed for Ca 2 La 3 Sb 3 O 14 upon excitation at 457 nm, attributed to [Eu3+-O2-] entities. • This feature is one of the most energetic 5D 0.→7F 0 lines reported in the literature for Eu3+ in an oxide host. [ABSTRACT FROM AUTHOR]