Thermodynamics of the Si-O-N system: II, Stability of Si sub 2 N sub 2 O(s) by high-temperature mass spectrometric vaporization

The Si sub 2 N sub 2 O(s) compound is vaporized in a multiple Knudsen cell connected to a mass spectrometer. Comparison of SiO(g) and N sub 2 (g) pressures between different samples in the Si-N-O system, as triphasic or diphasic mixtures from Si(s), Si sub 3 N sub 4 (s), and Si sub 2 N sub 2 O(s), allows determination of the SiO(g) evaporation coeff. and consequently the calculation of the equilibrium pressure of SiO(g). The standard enthalpy of formation of Si sub 2 N sub 2 O(s) is determined. 27 refs.