Thermodynamics of the Si-O-N system .2. Stability of Si2N2O(s) by high-temperature mass spectrometric vaporization

The Si2N2O(s) compound is vaporized in a multiple Knudsencell connected to a mass spectrometer, Comparison of SiO(g) and N-2(g) pressures between different samples in the Si-N-O system, as triphasic or diphasic mixtures from Si(s), Si3N4(s), and Si2N2O(s), allows the determination of the SiO(g) evaporation coefficient and consequently the calculation of the equilibrium pressure of SiO(g), Then the standard enthalpy of formation of Si2N2O(s) is determined: Delta(f)H degrees(m)(Si2N2O, s, 298.15 K) = -887.5 +/- 10 kJ . mol(-1).