The enthalpy of formation of hexagonal boron nitride

The energies of combustion in fluorine of three specimens of hexagonal boron nitride with different degree of ideal crystalline structure have been measured in a two-compartment calorimetric bomb at 298.15 K according to reaction: BN(cr) + 3/2F(2)(g) = BF3(g) + 1/2N(2)(g), and new standard molar enthalpies of formation Delta(f)H(m)(0) have been calculated and used to rank the samples in order of stability: Delta(f)H(m)(0) = -(245.8 +/- 1.1) kJ/mol for turbostratic sample, that deviates most from the crystalline structure; Delta(f)H(m)(0) -(248.5 +/- 0.9) kJ/mol for the sample with an interlayer spacing that is only about 0.5% larger than the ideal crystalline h-BN; and Delta(f)H(m)(0) = -(250.8 +/- 1.2) kJ/mol for crystalline h-BN.