Thermodynamics of the Si‐O‐N System: I, High‐Temperature Study of the Vaporization Behavior of Silicon Nitride by Mass Spectrometry

Si{sub 3}N{sub 4}(s) powders are vaporized in effusion cells, and the gaseous phase, analyzed by mass spectrometry, is composed of N{sub 2}, Si, Si{sub 2}, Si{sub 3}, SiN, and Si{sub 2}N. Owing to retarding vaporization of N{sub 2}, effusion cells with different orifice sizes are used in order to determine the evaporation coefficient for this species, which is then compared with previous Knudsen or Langmuir studies. Enthalpies of formation for SiN(g) and Si{sub 2}N(g) are determined.