Influence of ternary oxide additives on thermal conductivity of pressureless sintered Si3N4

Dense Si3N4 ceramic was fabricated by unimbedded pressureless sintering at 1650 degrees C with a short holding time of 1 h. The role of ternary oxide additives (Y2O3-MgO-SiO2 and Y2O3-MgO-ZrO2) on the phase and microstructure of Si3N4 and subsequently on thermal conductivity was examined. Y2O3-MgO-SiO2 additive facilitated alpha -> beta transformation better, whereas Y2O3-MgO-ZrO2 additive enhanced grain size (-40 %), which led to higher thermal conductivity (>1.5 times,-50 W/m center dot K). The influence of liquid phase viscosity on grain elongation was noteworthy. This study shows a cost-effective fabrication of highly-dense Si3N4 with desirable thermal conductivity.

Automated summary

Dense Si3N4 ceramic was fabricated by pressureless sintering, and the addition of ternary oxide additives was found to significantly affect the phase, microstructure, and thermal conductivity of the material.