Flash Sintering Of BaTiO₃ And High-Entropy Ceramics

Sintering is one of the most important processes in the preparation of advanced ceramics.It usually takes a long time at a higher temperature,and the whole process consumes energy and time.The flash sintering developed in recent years is a new electric field-assisted sintering technology,which can realize rapid densification sintering of ceramics at lower furnace telperature.In this paper,the flash sintering of BaTiO3 and 4 kinds of high-entropy ceramics has been studiedThe temperature-rising flash sintering of BaTiO3 is studied.It is found that the electric field can significantly reduce the sintering temperature of BaTiO3.The higher the electric field strength,the lower the flash sintering temperature and the smaller the grain size.The constant temperature flash sintering of BaTiO3 was studied.It was found that the grain size of BaTiO3 could be in the sub-micron scale when the fumace temperature was below 1000°C.The two-step flash sintering method and the two-step method based on flash sintering can effectively inhibit grain growth and improve the density.When TiO2 is added to BaTiO3.liquid phase will appear during flash sintering,but it is difficult to control the amount of liquid phase,which results in the bending of samples after flash sintering.The flash sintering of Ba(Ce0.2Hf0.2Sn0.2Ti0.2Zr0.2)O3 and Ba(Nb0.2Yb0.2Sn0.2Ti0.2Zr0.2)O3 high-entropy oxide ceramics was studied.It was found that the critical power consumption of Ba(Ce0.2Hf0.2Sn0.2Ti0.2Zr0.2)O3 was 150 mW/mm3,which was significantly higher than that of other materials(7-40 mW/mm3).The flash temperature of Ba(Ce0.2Hf0.2Sn0.2Ti0.2Zr0.2)O3 is slightly higher than that of Ba(Nb0.2Yb0.2Sn0.2Ti0.2Zr0.2)O3.Both high-entropy oxide ceramics are difficult to densify by flash sinteringFlash sintering of(Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)0 and(Ce0.2Zr0.2Hf0.2Sn0.2Ti0.2)O2 entropically stabilized oxide ceramics was studied.It was found that(Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)0 entropically stabilized oxide ceramics required less electric field intensity(40V/cm),and its voltage,current and power density fluctuated significantly during flash sintering.It was difficult to observe the "steady state" of flash sintering in common materials.This fluctuation can be effectively suppressed by increasing the current density,increasing the temperature of furnace temperature and prolonging the holding time.(Ce0.2Zr0.2Hf0.2Sn0.2Ti0.2)O2 entropically stabilized oxide only passes tlirough the middle part of the sample during flash sintering,resulting in local sintering of the material.