Silicon nitride can be processed in a green, biscuit or fully dense state. In a green or biscuit state, it is relatively easy to process to create complex geometric shapes. However, the sintering process required for complete compaction of the material results in a shrinkage of the silicon nitride body by about 20%.
This shrinkage means that very tight tolerances cannot be achieved when processing silicon nitride prior to sintering. In order to achieve very tight tolerances, the fully sintered material must be machined/ground with diamond tools. This process uses a very precise diamond-coated tool/wheel to remove the material until the desired shape is obtained. This can be a time-consuming and costly process due to the inherent rigidity and hardness of the material.
