Electric field and current-assisted ceramic processing: Origins and mechanisms

Ceramic components have mainly been manufactured by a sintering process, in which green compacts of ceramic raw powder are consolidated by exposure them to high temperatures for long periods. In contrast, electric field/current-assisted sintering, such as spark plasma sintering (SPS) and flash sintering, has been widely studied as an effective means of reducing the sintering temperature and time. In addition, the accelerating effect of an electric field on the dynamic behavior of ceramics, such as atomic (ion) diffusion and plastic deformation, is widely recognized. As in electroplasticity in metals and alloys, dislocation motion in oxide and chloride crystals is activated by the application of electric fields. Enhanced plastic deformability at high temperatures under strong electric fields has indeed been demonstrated for various polycrystalline ceramics. This technology has also recently proven applicable to high-speed sintering, sinter forging, joining, and even crack healing of ceramics. The dynamic behavior of ceramics accelerated by electric and current fields is not only theoretically significant but also practically important for developing innovative ceramic processing technologies. The present review summarizes the effects of electric field/current on the dynamic behavior of ceramics, directly relevant to high-temperature processes such as sintering densification, sinter forging, plastic forming and the joining of ceramic components. These electric field-assisted techniques are expected to contribute to the development of innovative ceramic manufacturing processes that enable high-speed, energy-saving, and environmentally friendly synthesis.