A novel thermally matched conductive phase of silicon nitride ceramics

Tungsten was first proposed as a conductive phase that better matches the thermal expansion of silicon nitride ceramics. Silicon nitride ceramics containing 20 vol% tungsten particles were fully densified via gas pressure sintering under a following nitrogen atmosphere. After introducing the tungsten particles, the thermal conductivity is increased two-fold and thermal expansion coefficient (CTE) almost remains as low as the monolithic silicon nitride ceramics. Most importantly, the composite ceramics achieve good electrical conductivity and a small and complex shape was machined via wire-electrode cutting to confirm its good wire-electrical discharge machinability. Tungsten particles have been proven to be a new ideal conductive phase for silicon nitride ceramics, and a new wire-electrical discharge machinable silicon nitride-based ceramic was prepared.