Densification Technology

During sintering of ceramic or metal powder compacts, the useful properties of the materials are developed and the part takes on its final shape. After sintering, only finishing processes, such as surface grinding or a follow-up heat treatment to remove residual stresses, may remain. Perhaps the most significant factor determining the rate of progress in densification technology has been the attainment of increasingly higher furnace temperatures, and the improved control of the furnace environment. Some structural ceramics, such as silicon carbide, require temperatures over 2000°C to get sufficient densification; other ceramics, such as zinc oxide varistors, require exceptionally close control of the sintering temperature to achieve optimum properties; in yet others, such as the lead zirconate titanate family of electrooptical and ferroelectric ceramics, the furnace atmosphere must be controlled to avoid evaporation of volatile constituents.