High-pressure synthesis and crystal structure of Al₃BO₆

Abstract Orthorhombic Al 3 BO 6 was synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 5 GPa and 1,200 °C, respectively. Its structure has been determined via single-crystal diffraction and is isotypic to M 3 BO 6 ( M = Cr, Fe) and homeotypic to the natural mineral norbergite (Mg 3 SiO 4 (OH) 2 ). Thereby, we could complement the first report of Al 3 BO 6 by Capponi et al. in 1972 (Capponi, J.-J.; Chenavas, J.; Joubert, J.-C. Eur. J. Mineral. 1972 , 95 , 412–417.) by providing a precise structure description. Al 3 BO 6 crystallizes in the space group Pnma (no. 62) with 4 formula units per unit cell and the lattice parameters a = 9.5060(5), b = 8.1058(4) and c = 4.2899(2) Å. Infrared spectroscopy (powder sample) and high-temperature X-ray powder diffraction further characterize the compound.