Nonstoichiometry as a hidden aspect of TbAl(BO) optical properties

TbAl 3 (BO 3 ) 4 should not be considered as a strictly stoichiometric compound. A variety of Tb 1+ x Al 3− x (BO 3 ) 4 ( x = −0.1-0.15) single phase compositions with the R 32 space group were synthesized in the TbBO 3 -(Al 2 O 3 ·B 2 O 3 ) system. The K 2 Mo 3 O 10 -B 2 O 3 -Al 2 O 3 flux was used to grow Tb 1+ x Al 3− x (BO 3 ) 4 ( x = 0.06 and 0.09) crystals. The orthoborates have typical luminescence in the green range which correlated with the 5 D 3 → 7 F 6 electron transition of Tb 3+ . However, deviating from stoichiometry can result in halving the quantum efficiency of luminescence. The SHG efficiency from 1064 nm radiation for Tb 1+ x Al 3− x (BO 3 ) 4 crystals ( x = 0.06 and 0.09) was found to be 1.82 and 1.53 times higher than that of KDP, respectively. TbAl 3 (BO 3 ) 4 was found to exist in a range of solid solutions. Its stoichiometric composition shows the best optical properties.