Fundamentals and future prospects of flash sintering of advanced ceramics

Abstract

Electric field-assisted sintering, in which mechanical pressure is often combined with DC or AC electric field to enhance densification of ceramics and ceramic composites, is gaining interest in recent decades due to the accelerated consolidation compared to conventional, pressureless sintering. In particular, flash sintering, where densification occurs almost immediately (typically < 5 seconds) under a threshold condition of temperature and applied DC electric field, has attracted extensive attention as an innovative sintering method since 2010. It is advantageous that the configuration of apparatus for flash sintering is rather simple in comparison to usual electric field-assisted sintering methods. The flash sintering has been demonstrated in various oxide/non-oxide ceramics, and mechanism of such a dynamic phenomenon has been investigated. The flash sintering event is characterized by an abrupt densification at relatively low temperature and a nonlinear increase in electric conductivity at the occurrence of the flash sintering. Joule heating therefore plays a key role in the flash event. In the present paper, typical examples of flash sintering and advantages of the novel technique are briefly summarized, and recent results of creating new materials and microstructures are introduced.