Thermal conductivity of pressureless sintered Si3N4 ceramics with Li-exchanged zeolite

The effects of temperature on the thermal conductivity of Si3N4 sintered with Li-exchanged zeolite were investigated. The highest conductivity was measured for the ceramics sintered with 10 % of additive. The complete a->b-Si3N4 transformation and maximum density (> 98 % TD) were attained with the sample sintered at 1650 ºC. However, the results show that Al and O from the additive dissolve into the b-Si3N4 structure which act as phonon scattering sites resulting in a lowering of the conductivity and a weaker temperature dependance of the conductivity.