High Temperature Vapor Pressure of Si

抄録

The vapor pressures of Si(g) and Si₂(g) over Si(l) were measured with a time-of-flight mass spectrometer equipped with a boron-nitride Knudsen cell. The equations for the vapor pressure of Si(g) and Si₂(g) obtained by the least squares treatment were given as follows:
log(P_Si/Pa)=(-2.08±0.10)×10⁴K/T+(10.84±0.53)
log(P_Si2/Pa)=(-2.46±0.09)×10⁴K/T+(10.93±0.47)
The vaporization enthalpy of Si(g) at the standard state (409.2±2.3 kJ mol^-1) calculated based on the third law was in good agreement with the second law one (407.4±19.1 kJ mol^-1). The third law value of the vaporization enthalpy of Si₂(g) at the standard state (493.7±1.9 kJ mol^-1) was also in good agreement with the second law one (491.5±15.7 kJ mol^-1). The dissociation energies of Si₂(g) calculated from the vaporization enthalpy of Si(g) and Si₂(g) at the standard state were 323.3±31.2 kJ mol^-1 (the second law value) and 324.7±3.8 kJ mol^-1 (the third law value).