BaO−B ₂ O ₃ system and its mysterious member Ba ₃ B ₂ O ₆

Abstract

Abstract The first systematic study of the BaO–B 2 O 3 system and barium orthoborate Ba 3 B 2 O 6 (3BaO·B 2 O 3 ) was reported in 1949. Thereafter, the system was repeatedly refined but the structure of Ba 3 B 2 O 6 compound has not been adequately studied yet. In our study we have, for the first time, obtained the crystalline samples of Ba 3 B 2 O 6 . The solved structure ( Pbam , a = 13.5923(4) Å, b = 13.6702(4) Å, c = 14.8894(3) Å) belongs to the class of ‘anti‐zeolite’ borates with a pseudotetragonal [Ba 12 ( BO 3 ) 6 ] 6+ cation pattern which contains channels along the c axis filled with anionic clusters. The Ba 3 B 2 O 6 compound may be regarded as a fluorine‐free end‐member of the Ba 3 ( BO 3 ) 2– x F 3 x solid solution. The BaO–B 2 O 3 phase diagram presented in our study is based on our research and literature data.