The standard molar enthalpies of formation of α−Si3N4 and β−Si3N4 by combustion calorimetry in fluorine, and the enthalpy of the α-to-β transition at the temperature 298.15 K

Abstract
The standard molar enthalpies of formation ΔfH°m of α−Si3N4 and β−Si3N4 have been determined by fluorine combustion calorimetry: ΔfH°m (Si3N4, cr, α, 298.15 K) = − (828.9 ± 3.4) kJ · mol−1 and ΔfH°m (Si3N4, cr, β, 298.15 K) = – (827.8 ± 2.5) kJ · mol−1. These results indicate that the enthalpy of the α-to-β transition, approximately (1 ± 4) kJ · mol−1, is negligible within experimental uncertainty.