Fig. (3)
The PL spectra of the Ba
3
LaTa
3
O
12
(1,5), Sr
3
LaTa
3
O
12
(2,6), Ba
3
LaNb
3
O
12
(3) and Sr
3
LaNb
3
O
12
(4,7). T = 8 K; E
ex
= 6.2 (1 – 4), 4 eV (5 -7) for the left part of the Figure; E
ex
= 5 eV for the right part of the Figure.