Effect of electric fields and current on ceramic processing

Strong electric field/current is known to accelerate high temperature processing of ceramic materials. For example, pulsed electric current sintering, that is called Spark-Plasma-Sintering (SPS), has widely been known as a fast-sintering technique that utilizes electric current effect.

In recent decade, flash event that takes place under strong electric fields have attracted many attentions as another fast-sintering technique because it can accelerate the sintering of ceramic powders without pressure. The flash event has firstly been reported by Raj and his colleagues in sintering phenomena, but it is now reported that it can accelerate not only the sintering behavior of powders, but also high temperature bulk phenomena, such as deformation, joining and crack healing.

Although current assisted processing has been explained that electric field/current contributes to the acceleration of diffusivity of ceramics, the details are still under discussion. For the flash sintering, however, the phenomena have generally completed within a few seconds. The steep behavior that completes within a few seconds is an advantage for industrial applications, but it makes it difficult to discuss the rate-controlling mechanisms of the current assisted phenomena.

In this work, therefore, the current effects during the flash event were examined in the bulk state of polycrystalline zirconia ceramics (8YSZ) as a reference material. As a result, it can be confirmed that the high temperature processing, such as grain growth and deformation, can be accelerated under the flash event through enhanced grain boundary diffusivity caused additionally by the non-thermal effect of the flash event.

In the presentation, the more detailed field/current dependent high temperature processing will be reported.

Speaker

Koji Morita is Group Leader of the Polycrystalline Optical Material Group at the Research Center for Electronic and Optical Materials, National Institute for Materials Science (NIMS) - Tsukuba, Japan.

After receiving his Ph.D. in Materials Science and Technology from Kyushu University in 1997, he joined NIMS, where he has since conducted research on advanced oxide ceramics.

His research focuses on high-temperature phenomena in ceramic materials, including superplasticity, creep deformation, sintering, and transparent ceramics. More recently, his work has concentrated on the fabrication of transparent oxide ceramics using Spark Plasma Sintering (SPS) and on understanding the effects of electric current on high-temperature deformation and sintering processes. He has authored approximately 200 scientific publications and has received several prestigious awards from leading Japanese materials and ceramic science societies.