Boron suboxide (860) was synthesized by reacting boron and boric acid (H(3)BO(3)) at pressures between 1 and 10 GPa, and at temperatures between 1300 and 1400 degrees C. The B(6)O samples prepared were icosahedral with diameters ranging from 20 to 300 nm. Well-crystallized and icosahedral crystals with an average size of similar to 100 nrn can be obtained at milder reaction conditions (1 GPa and 1300 degrees C for 2 h) as compared to previous work. The bulk B(6)O sample was stable in air at 600 degrees C and then slowly oxidized up to 1000 degrees C. The relatively mild synthetic conditions developed in this study provide a more practical synthesis of B(6)O, which may potentially be used as a substitute for diamond in industry as a new superhard material. (C) 2011 Elsevier Ltd. All rights reserved.