Effect of zinc oxide doping on the grain boundary conductivity of Ce _0.8Ln_0.2O_1.9 ceramics (Ln = Y, Sm, Gd)

The effect of zinc oxide (ZnO) doping on the densification behaviours and the electrical properties of Ce_0.8Ln_0.2O_1.9 (Ln = Y, Sm, Gd) ceramics are examined. The addition of ZnO (1 mol%) reduces the sintering temperature by ∼200 °C and improves the grain boundary behaviours significantly. Both the apparent grain boundary conductivity (σgbapp) and the specific grain boundary conductivity (σgbsp) are investigated. Under the same synthetic conditions, ZnO doping leads to a larger grain size and a higher σgbsp. The SEM and EDS results indicate that ZnO-doping can induce Si enrichment on the surfaces of samples (i.e. reducing the content of Si at grain boundaries), which may explain the improvements occurs in the grain boundary conductions.