Preparation yttria-stabilized zirconia electrolyte by spark-plasma sintering

Miscellaneous sintering conditions of spark-plasma sintering (SPS) were investigated to obtain high-density yttria-stabilized zirconia (YSZ) electrolytes for solid oxide fuel cells (SOFC). Nano-size YSZ raw powder (50 nm) was densified to a relative density of 99.1% at 1400 °C, with an applied uniaxial pressure of 23 MPa, and a total of four consecutive sintering cycles at 3 min per cycle. Impedance spectroscopy was used to elucidate the electrical properties of the YSZ electrolyte. It was found that SPS could significantly improve the ionic conductivity of the YSZ electrolyte over conventional sintered (using an electrical resistance furnace) samples at similar sintering temperatures. These phenomena were due to the diverse microstructures obtained by SPS samples as compared to the conventional sintered samples. For SPS samples, most of the pores were found to exist within the grains. While for the conventional sintered sample, most of the pores were encountered at the grain boundaries, which would significantly increase the grain boundary resistance in the samples.