STRUCTURE AND BULK MODULUS OF HIGH-STRENGTH BORON-COMPOUNDS

The structures and homogeneity ranges of B6O1-x and B12S2-x were studi ed using Rietveld analysis of powder X ray patterns. The oxygen conten t of boron suboxide decreases with temperature int the range 1250-1450 degrees C, Stoichiometric boron suboxide cannot be prepared from amor phous or alpha-rh boron and B2O3 at ambient pressure. Significantly hi gher pressures are required, The boron subsulfide was found to be stab le from B12S<1 to B12S1.3 at 1400-1600 degrees C. Semiempirical bulk m odulus calculations are reported for hard icosahedral boron-rich compo unds and diamond-like tetrahedrally coordinated boron compounds. In co nnection with this the structure of diamond-like B2O is discussed. (C) 1997 Academic Press.