From BaAlBO3F2 to BaAlB3O6F2 and BaAl2(B3O6)2F2: the Enhancement of Birefringence and Band Gap by Extending the π-Conjugated System Combined with [Al-O/F] Functional Groups

Two new fluoroaluminoborates, BaAlB 3 O 6 F 2 and BaAl 2 (B 3 O 6 ) 2 F 2 , were designed and synthesized, exhibiting a markedly elevated birefringence in comparison with BaAlBO 3 F 2 .