Microstructural evolution of 3YSZ flash‐sintered with current ramp control

Abstract

The effect of a controlled current ramp during flash sintering (FS) on the densification and microstructural evolution of 3 mol% yttria‐stabilized zirconia was investigated. The samples were flash sintered using a current ramp control with six different current ramp rates and compared with samples sintered by FS without current ramp control. In both cases, maximum electric current densities of 100 and 200 mA mm−2 were used. The microstructure of cylindrical samples was observed, showing grain size heterogeneity between the curved surface and the core for the flash‐sintered (FSed) samples regardless of the maximum current density used. By contrast, the current ramp FSed samples exhibited a homogeneous grain size when the electric current density of 100 mA mm−2 was applied. Thus, controlling a current ramp during FS can be an alternative for avoiding grain size heterogeneity on ceramics sintered by this technique.

Flash sintering of yttria‐stabilized zirconia powders coated with nanoscale films of alumina by atomic layer deposition

“…Alternatively, a current rate experiment 12 can be conducted where the current is increased at a constant rate. These samples reach high final densities and have greater microstructural homogeneity as compared to samples sintered using voltage‐to‐current control experiments 12‐14 . The time span of the current rate experiments can be stretched, which can provide greater insights into the densification mechanism.…”

“…These samples reach high final densities and have greater microstructural homogeneity as compared to samples sintered using voltage-to-current control experiments. [12][13][14] The time span of the current rate experiments can be stretched, which can provide greater insights into the densification mechanism. Joule heating and avalanches of Frenkel defects, in concentrations far from equilibrium, have been suggested as the possible mechanisms for flash sintering.…”

Promoting microstructural homogeneity during flash sintering of ceramics through thermal management

“…73 Current limit stepping via PID has been built into FS protocols 74 and resulted in superior homogeneity between the surface and core. 75 The use of the current ramp FS approach also resulted in a smaller anode/ cathode grain size difference in 3YSZ. 41 To provide reproducibility and control required to adapt FS to industrial applications, Lucideon Ltd. has developed a control system based on a nonlinear algorithm.…”

Shrinkage rate control during a flash state by current‐ramping for 3 mol% Y2O3‐doped ZrO2 polycrystals

“…In their technique, the power spike, which is common in voltage-to-current experiment, is largely decreased. Their technique including other studies 12,[14][15][16][17][18] suggests new possibilities of tuning properties such as microstructure, electric properties, and so on. From a viewpoint of a sintering technique, it is attractive to apply the current control technique to flash sintering in…”