Sintering Kinetics of Beryllia

Compacts of sulfate‐derived beryllia were sintered, for various times, in nitrogen at 1050° to 1500°C. The applicable equation for densification is image This is predicted by the Coble intermediate‐stage volume diffusion sintering model for material showing the observed (time) ½ dependence of grain size on time. Apparent diffusion coefficients for sintering are near those for oxygen diffusion in BeO but it is not possible to make a firm conclusion on the rate‐controlling ionic species. The activation energy for diffusion differs from that for grain growth; therefore the relation between porosity and grain size is not independent of temperature. Mathematical analysis shows that under certain conditions there may be an optimum temperature at which a required density can be attained with a minimum grain size.