Overcoming the effect of contaminant in solid oxide fuel cell (SOFC) electrolyte: spark plasma sintering (SPS) of 0.5 wt.% silica-doped yttria-stabilized zirconia (YSZ)

The alleviation of SiO 2 as contaminant in SOFC electrolyte was studied through spark plasma sintering (SPS) of yttria-stabilized zirconia (YSZ) doped with ∼0.5 wt.% SiO 2. The outcome of variations in SPS process conditions such as sintering temperature, duration, and applied pressure on the grain boundary and grain interior resistivity of silica-doped YSZ electrolyte was studied with ac impedance spectroscopy. Results show that the apparent grain boundary resistivity of SPS-processed silica-containing YSZ electrolyte is moderately higher than that of pure YSZ electrolyte, but it was significantly lower than that of silica-containing YSZ electrolyte prepared by conventional sintering. A linear correlation was observed between relative density and grain interior resistivity, no matter what sintering method or starting powder was adopted. Furthermore, the apparent grain boundary resistivity was found to be strongly dependent on the grain size and the effective conducting area of the grain boundary. Results showed that SPS was an efficacious powder consolidation method, and it could effectively shorten the sintering duration down to several minutes. It was also found to significantly reduce the grain boundary resistivity without detrimental consequence on the grain interior resistivity. This raised the prospect of scavenging the detrimental effects of contaminants in SOFC electrolyte through SPS processing.