Crystal Structure of c‐M₅B₁₂O₂₅(OH) (M=Al, Al/Ga, Ga/In) – Three Disordered Cubic Trielborates Synthesized under High‐Pressure Conditions

Abstract

The isotypic trielborates c-Al 5 B 12 O 25 (OH), c-Al 1.7 Ga 3.3 B 12 O 25 (OH), and c-Ga 4 InB 12 O 25 (OH) were synthesized under high-pressure/ high-temperature conditions of � 12 GPa and � 1100°C. The three cubic compounds crystallize in the space group Fm � 3m with Z = 4 and a = 10.8226(5), 10.9258(5), and 11.176(2) Å for c-Al 5 B 12 O 25 (OH), c-Al 1.7 Ga 3.3 B 12 O 25 (OH), and c-Ga 4 InB 12 O 25 (OH), respectively. The crystal structures of all three compounds were determined by single-crystal X-ray diffraction revealing disordered cubic structures composed of MO 6 octahedra (M = Al, Al/ Ga, Ga, In) and BO 4 tetrahedra. Single-crystal Raman and IR spectroscopic data further characterize the compounds, and the latter confirms the presence of hydroxyl groups.