Fig. (3) The PL spectra of the Ba3LaTa3O12 (1,5), Sr3LaTa3O12 (2,6), Ba3LaNb3O12 (3) and Sr3LaNb3O12 (4,7). T = 8 K; Eex = 6.2 (1 – 4), 4 eV (5 -7) for the left part of the Figure; Eex = 5 eV for the right part of the Figure.