SYNTHESIS AND STRUCTURE OF NONSTOICHIOMETRIC B6O

Boron suboxide B6O1-x was synthesized from a mixture of amorphous boro n or alpha-rhombohedral boron and B2O3 in excess (nominal composition B3.33O). The use of alpha-boron resulted in a more completely crystall ized boron suboxide, which was utilized to study the homogeneity range of the suboxide in the temperature range 1250 degrees C-1450 degrees C. The oxygen content of solid B6O1-x was determined from Rietvelt ana lysis of X-ray powder diffraction intensities. The oxygen content decr eased from 12.3 at% at 1250 degrees C to 11.6 at% at 1450 degrees C. I t is probable that stoichiometric B6O (14.3 at% oxygen) can only be pr epared at pressures considerably higher than ambient pressure. (C) 199 7 Elsevier Science S.A.