Effect of Y2O3 on the Si3N4- carbon interaction at high temperatures

The method of pulsed reduction extraction in a flow of carrier gas is used to study the effect of Y2O3 on the interaction between Si3N4 and carbon in the range of 1500–3500°C. High-temperature dependences of the degree of extraction of oxygen (in the form of CO) and nitrogen from Si3N4, Y2O3, and a proportioned mixture of them (from 2 to 5% Y2O3 ) are obtained. It is established that small additives of Y2O3 diminish substantially the thermal stability of Si3N4. It is assumed that Y2O3 has a pseudocatalytic effect on the Si3N4 — carbon interaction at high temperatures. The Temkin — Shvartsman method and published values of the Gibbs free energy are used for thermodynamic calculation of the change in the Gibbs free energy for evaluation of the possibility of some hypothetical reactions.