Effect of sintering aids on the conductivity of BaCe0.9Ln0.1O3−δ

Polycrystalline powders of BaCe0.9Ln0.1O3−δ (Ln = La, Nd, Sm, Gd, Yb, Tb and Y) have been prepared using a freeze-drying precursor route at 1000 °C. In order to decrease the densification temperature, different sintering aids (e.g. Co, Zn, Ni, Fe and Cu) were added by mixing the polycrystalline powders with a nitrate solution containing these metals. This allows obtaining dense ceramics at temperatures as low as 1000 °C, when compared to samples without sintering aids at 1400 °C. The effect of aid content and sintering temperature on the microstructure and electrical conductivity were investigated by scanning electron microscopy and impedance spectroscopy. The addition of small amounts of transition metals does not produce observable structural changes by conventional X-ray powder diffraction. However, the bulk and total conductivities decrease when compared to samples without transition metals. Zn seems to be the most effective sintering element for BaCe0.9Ln0.1O3−δ electrolytes because it does not cause significant changes in the ionic and electronic conductivities.

► BaCe0.9Ln0.1O3−δ (Ln = La, Nd, Sm, Gd, Yb, Tb and Y) prepared by freeze-drying. ► Densification temperature by using different sintering aids (e.g. Co, Zn, Ni, Fe and Cu) was as low as 1000 °C. ► These transition metals decrease both the bulk and grain boundary conductivity of barium cerates. ► Zn produces minor changes in the ionic conductivity of barium cerates.