Crystal structure and thermal behavior of Cs2Ca[B4O5(OH)4]2·8H2O

Abstract Dicesium calcium tetraborate octahydrate, Cs 2 Ca[B 4 O 5 (OH) 4 ] 2 ·8H 2 O, was prepared in molar ratios Cs 2 O:B 2 O 3 :CaCl 2 = 1:2:1 and its structure has been determined by single-crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group P2 1 2 1 2 1 with unit cell dimensions, a =11.531(2) A, b =12.855(2) A, c =16.803(4) A; V =2490.7(8) A 3 , Z =4. The structure contains alternate layers of tetraborate ions and two of the water molecules, along with the cations and remaining water molecules. The isolated [B 4 O 5 (OH) 4 ] 2− is constructed from two BO 3 (OH) tetrahedron groups and two BO 2 (OH) triangular groups which have only corners in common. The Ca 2+ ion displays seven coordination, while two non-equivalent Cs + ions display 11 and 9 coordination, respectively. The dehydration of this hydrated double borate occurs in one step and leads to an amorphous phase which undergoes a crystallization.