Results are given for the first time of experimental investigations of
the parameters of melting and thermodynamic stability of silicon nitr
ide in the temperature range of 1300 - 4000 K under an ambient gas pre
ssure of 10 - 200 MPa. The melting temperature of silicon nitride in t
he range of gas pressure of 120 - 198 MPa is shown to vary from 2560 t
o 2775 K.