Reactive flash sintering: Assessing the role of volume change during phase reaction

Abstract

Reactive flash sintering (RFS) has recently emerged as a novel technique for simultaneous synthesis and densification of ceramics where phase reaction and sintering occur in a few seconds. Typically, any phase reaction is accompanied by a volume change. This work is an initial attempt to understand the influence of phase-reaction-driven volume change on densification during RFS. We carried out RFS on two systems; one showing large volume contraction ($BaO+Ti{O}_2\to BaTi{O}_3$) and other showing large volume expansion ($A{l}_2{O}_3+Ti{O}_2\to A{l}_{2}Ti{O}_5$), during phase reaction. The progress of phase reaction and corresponding densification was quantitatively monitored through XRD, real-time video and density measurement of interrupted experiments. In the volume expansion system, the phase reaction contributed positively to densification. In the volume contraction system, phase reaction de-sintered the sample by generating additional pores. We show that volume change associated with phase reaction significantly influences the extent of sintering during the RFS process.