Effect of large β-Si3N4 particles on the thermal conductivity of β-Si3N4 ceramics

Mean-field micromechanics model, the rule of mixture is applied to the prediction of the thermal conductivity of sintered β-Si3N4, considering that the microstructure of β-Si3N4 is composed of a uniform matrix phase (which contains grain boundaries and small grains of Si3N4) and the purified large grains (⩾2 μm in diameter) of Si3N4. Experimental results and theoretical calculations showed that the thermal conductivity of Si3N4 is controlled by the amount of the purified large grains of Si3N4. The present study demonstrates that the high thermal conductivity of β-Si3N4 can be explained by the precipitation of high purity grains of β-Si3N4 from liquid phase.