Sintering is a production process for forming a mechanically strong body out of a ceramic or metallic powder. This is achieved by applying heat (often in combination with higher pressure) but keeping the temperature below the melting temperature of the main component. During sintering, shrinkage due to compaction and pore healing is usually observed. In addition, grain growth may occur. A distinction is made between solid-phase and liquid-phase sintering. For the latter, only partial melting takes place during heating.
The steps occurring during sintering are very complex. There are different factors that influence the sintering process like grain size or compaction. In addition, the conditions during sintering (temperature, time, and atmosphere) will also have an influence on the final product.
Sintering follows debinding as the next step in the production chain. It is typically studied with a dilatometer to acquire information about shrinkage steps and final shrinkage. Another method of characterizing the sintering process is thermal conductivity, as neck formation and grain growth can result in a different thermal conductivity than a loose or just compacted powder.
As sintering takes usually place at higher temperatures, energy costs are high. Therefore, different approaches like Rate Controlled Sintering (RCS) or Kinetic Analysis are used to reduce time and if possible, also temperature, and additionally to optimize the densification of the sintered part.
See below for an example depicting the sintering of a porcelain green body.