Research On Temperature Field Of 8YSZ Ceramics During Flash Sintering

Ceramic materials have a series of excellent properties.But the conventional sintering technology requires high sintering temperature and takes a long time.Developing new sintering technology has always been an important research topic in the field of ceramics to reduce costs and improve the properties of ceramics.The recently introduced ceramic flash sintering technology has been paid more and more attention due to their low sintering temperature and fast densification.With this approach,a series of ceramic have been sintered.However,there is a very limited understanding on the mechanism of the flash sintering so far.In this paper,the temperature variation of the sample surface during the flash sintering has been studied,the deficiency of joule heating theory is demonstrated,and a reasonable explanation is proposed to expand our knowledge on the mechanism of the flash sintering.Using dense 8YSZ ceramic,the influences of the electric field strength and DC electric current density on the flash sintering are explored.As the same time the effects of the AC electric field strength,electric current density and frequency on the flash sintering are investigated.Then,the temperature variation and temperature distribution of the sample surface are characterized during the flash sintering under the DC and AC fields by the infrared camera.The main conclusions can be drawn as follow:(1)With the DC field,the electric field strength affects the incubation time during the flash sintering.The higher electric field strength will shorten the incubation time.The electric field strength also affects the heating rise rate in the incubation stage.At the same electric current density,the higher electric field strength leads to the quicker heating rise rate.The electric field strength has no effect on the temperature in the stable stage.However,the electric current density affects the temperature in the stable stage.The higher electric current density causes the higher temperature.(2)With the DC field,the temperature of the sample surface is distributed asymmetrically.The temperature of anode is higher than the cathode sides.The highest temperature appears in 3/4 away from the cathode end.This unique temperature distribution is the result of the combined effects of the joule heating,interior defect reaction and electrode reaction.(3)With the AC field,the electric field strength also affects the incubation time of the flash sintering.The higher electric field strength will shorten incubation time and higher heating rise rate.The electric current density affects the temperature in the stable stage.The higher electric current density causes the higher temperature,and the higher frequency leads to the shorter incubation time.(4)With the AC field,the temperature of the sample surface is distributed symmetrically.The variation of the electric field strength is presented as the sine curve,which leads to the same joule heating,interior defect reaction and electrode reaction of the both sides.Therefore,the temperature of the sample surface is distributed symmetrically.