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

Abstract

• Role of ternary oxide additives on Si 3 N 4 microstructure and thermal conductivity. • Y 2 O 3 -MgO-ZrO 2 additive results ∼40% higher Si 3 N 4 grain size than Y 2 O 3 -MgO-SiO 2 . • Higher thermal conductivity (>1.5 times) for Si 3 N 4 with Y 2 O 3 -MgO-ZrO 2 additive. Dense Si 3 N 4 ceramic was fabricated by unimbedded pressureless sintering at 1650°C with a short holding time of 1h. The role of ternary oxide additives (Y 2 O 3 -MgO-SiO 2 and Y 2 O 3 -MgO-ZrO 2 ) on the phase and microstructure of Si 3 N 4 and subsequently on thermal conductivity was examined. Y 2 O 3 -MgO-SiO 2 additive facilitated α→β transformation better, whereas Y 2 O 3 -MgO- ZrO 2 additive enhanced grain size (∼40%), which led to higher thermal conductivity (>1.5 times, ∼50 W/m∙K). The influence of liquid phase viscosity on grain elongation was noteworthy. This study shows a cost-effective fabrication of highly-dense Si 3 N 4 with desirable thermal conductivity.