High-pressure/high-temperature syntheses of the new borate NiB ₆ O ₈ (OH) ₄

Abstract Explorative high-pressure/high-temperature syntheses (9 GPa, 1,200 °C) starting from NiO and H 3 BO 3 yielded a product mixture containing single crystals of NiB 6 O 8 (OH) 4 , a new orthorhombic borate (space group Fdd 2) with the lattice parameters a = 39.097(4) Å, b = 4.3880(4) Å, c = 7.5899(8) Å, V = 1,302.1(2) Å 3 , and eight formula units per cell. This compound is the third one in the structural class of borates with the general formula M (B 6 O 9– x )(OH) 3+ x ( M = In 3+ , Sc 3+ ( x = 0), Ni 2+ ( x = 1)). The reaction product has been studied by means of powder X-ray diffraction, and an infrared spectrum of a single crystal has been recorded. Results of BLBS and CHARDI calculations are presented.