Microstructure evaluation of 3YSZ sintered by Two-Step Flash Sintering

Abstract Flash Sintering (FS) is an energy-efficient sintering technique, which allows a considerable reduction in processing time and temperature. However, a recurring problem of flash sintered samples is the microstructural heterogeneity, which occurs mostly on samples with a high surface-to-volume ratio (e.g., cylindrical samples). Thus, aiming to obtain homogeneous microstructures and smaller grain sizes, this work evaluated the application of Two-Step Flash Sintering (TSFS) in 3YSZ and compared them with samples sintered by FS. The TSFS experiments consisted of applying a first step of current density with greater magnitude (100 mA mm-2 and 200 mA mm-2) followed by the second step with smaller magnitude (50 mA mm-2 and 75 mA mm-2). In the FS experiments, a single step of current density was used (100 mA mm-2 and 200 mA mm-2). The Results showed that TSFS significantly reduced the microstructural heterogeneity compared to FS, promoting smaller and more homogeneous grain sizes in different regions of the samples.