Dissolution Kinetics of β‐Si3N4 in an Mg‐Si‐O‐N Glass

Publisher Website
Google Scholar
Abstract
The rate of dissolution of β‐Si3N4 into an Mg‐Si‐O‐N glass was measured by working with a composition in the ternary system Si3N4‐SiO2‐MgO such that Si2N2O rather than β‐Si3N4 was the equilibrium phase. Dissolution was driven by the chemical reaction Si3N4(c)+SiO2(l)→Si2N2O(c). Analysis of the kinetic data, in view of the morphology of the dissolving phase (Si3N4) and the precipitating phase (Si2N2O), led to the conclusion that the dissolution rate was controlled by reaction at the crystal/glass interface of the Si3N4, crystals. The process appears to have a fairly constant activation energy, equal to 621 ±40 kJ‐mol−1, at T=1573 to 1723 K. This large activation energy is believed to reflect the sum of two quantities: the heat of solution of β‐Si3N4 hi the glass and the activation enthalpy for jumps of the slower‐moving species across the crystal/glass interface. The data reported should be useful for interpreting creep and densification experiments with MgO‐fluxed Si3N4.

This publication has 17 references indexed in Scilit: