Micro-thermal analysis of thermal conductance distribution in advanced silicon nitrides

A micro-thermal analysis technique was applied to investigate advanced silicon nitride materials, which exhibit high thermal conductivity. Local thermal properties in the microstructure were evaluated, and the grain boundaries were observed to have lower thermal conductance than the Si₃N₄ grains. It was found that thermal conductance both in the grains and boundaries was lowered by the addition of the sintering aid Al₂O₃, which is soluble in Si₃N₄ grains. This indicates that high thermal conductivity in silicon nitride ceramics is achieved both by grain growth, leading to a reduction in boundary density, and by eliminating soluble elements in silicon nitride grains. This revised version was published online in August 2006 with corrections to the Cover Date.