Structures and properties of layered barium borates Ba0.975[B6O9(OH)(O0.975Br0.025) · B2O(OH)3], Ba2[B5O8(OH)2](OH), Na2Ba2[B20O34(OH)4], and Ba5[B20O33(OH)4]H2O

Abstract

A new hexaborate, Ba 0.975 [B 6 O 9 (OH)(O 0.975 Br 0.025 ) · B 2 O(OH) 3 ], was synthesized under hydro thermal conditions. This compound is structurally similar to tunnelite and the synthetic borates Pb[B 6 O 10 (OH) · B 2 O(OH) 3 ], Pr[B 6 O 10 (OH) · B 2 O(OH) 4 ], and Nd[B 6 O 10 · B 3 O 3 (OH) 4 ] · H 2 O studied ear lier. In the new hexaborate and the refined pentaborate Ba 2 [B 5 O 8 (OH) 2 ]OH, in which the polyanions adopt an orientation in layers unusual for pentaborates, thermal vibrations of the terminal groups were revealed. This fact reflects the real crystal structure. The nonlinear optical properties of the crystals of the polar pent aborate Na 4 Ba 4 [B 20 O 34 (OH) 4 ] were determined. The crystal structure of the related pentaborate Ba 5 [B 20 O 33 (OH) 4 ]H 2 O was considered. The factors most likely responsible for the difference in the second harmonic generation signal for this pair were revealed.

Polytypism of Compounds with the General Formula Cs{Al2[TP6O20]} (T = B, Al): OD (Order-Disorder) Description, Topological Features, and DFT-Calculations

“…Borophosphates (as well as borophosphate ceramics and glasses) attract interest because of their wide technological applications as materials with optical [1][2][3][4][5], electrochemical [6][7][8][9], magnetic [10][11][12], and catalytic [13][14][15] properties. Moreover, crystalline borophosphates and metal borophosphates with microporous structures are considered as zeolite-like materials [16][17][18][19][20]. Borophosphates are characterized by a wide diversity of tetrahedral and mixed triangular-tetrahedral anionic motifs [21][22][23][24], owing to the different possible coordination environments of boron.…”