Effect of precursor particle size of NiO-YSZ electrodes in its physico-chemical and electrical conductivity properties for solid oxide electrochemical cells

Abstract

Electrodes play an important role in the overall performance of solid oxide electrochemical cells (SOC), such as for fuel cell or electrolysis cell applications. Desirable properties of the electrode include good morphological features with high electronic and ionic conductivity. In this study, in order to investigate the effect of precursor particle size on the microstructure and conductivity properties of nickel oxide and yttria-stabilized zirconia (NiO-YSZ), precursors were prepared with different particle sizes using a planetary ball mill via varying the milling speed and milling time. From the particle size analysis (PSA) of the milled samples based on the studied milling parameters, it was observed that the milling time had a significant effect on the resulting ball-milled samples compared to the effect of the milling speed. However, upon sintering to obtain the NiO-YSZ electrode composites, the effect of milling speed, in terms of grain size, can be observed. From the XRD patterns, major peaks can be attributed to cubic phases of NiO and YSZ; however, traces of ZrO2 impurity peaks can be seen for the precursor sample with higher milling speed. SEM-EDX analyses support the more agglomerated morphology for the sample with longer milling duration and larger grains for those with higher milling speed. The obtained total bulk conductivities for the sample milled at 400 rpm (10 h) is about 1.27x10-1 S/cm, and for the 400 rpm (20 h) is about 1.77x10-1 S/cm with Ea of 0.88 eV and 0.27 eV, respectively.