## 3 Results and Discussion
Figure 3: Electron-dispersive spectroscopy (EDS) mapping of as sintered NiO/ScSZ (top images) and reduced Ni/ScSZ (bottom image) for a g/n ratio of 0.27, showing the elemental map of Zr, Sc, Ni, and Q.  
Figure 2: Scanning electron microscopy (SEM) micrographs at 10,000\(\times\) magnification for sintered NiO/ScSZ (top) and reduced Ni/ScSZ (bottom) using g/n ratios of (**a,e**) 0.27, (**b,d**) 0.54, and (**c,f**) 1.1. Although from Figure 3, the Ni phase seems to agglomerate, the high magnification SEM images in Figure 4 clearly reveal that some nanoparticles of Ni are attached at the surfaces of the micrograined size ScSZ apart from the agglomerated ones. These Ni nanoparticles can be observed as fine yellow dots in the EDS mapping in Figure 3. This particular morphology may be important in increasing the triple-phase boundary (TPB) reaction sites. For SOEC applications, the TPB is an important site as this is a region of contact for the steam gaseous phase, ion conducting electrolyte phase, and electronic conducting electrode phase and where the reaction occurs. For this particular electrode material for SOEC, ScSZ is the ion conducting phase, the pore is where the gaseous steam flows in, and Ni is the electron- conducting electrode phase and a catalyst. Hence, the rate of the chemical reaction is proportional to the number of these active TPBs. Though the Ni particles appeared to be somewhat agglomerated, as shown in the EDS map in Figure 3, there are scattered Ni nanograins or nanoparticles situated at the surfaces of ScSZ grains, as revealed in Figure 4. Although the Ni nanoparticles are not connected, if electronic conductivity exists within the electrode, or such nanoparticles are connected or can be connected to the current collector, these nanoparticles that also act as a catalyst may play an important role and may contribute to the active TPBs. From the conductivity results in this study, it seems that the total conductivity of the electrode (Ni/ScSZ) is dominated by electronic conduction with the low activation energy (Figure 6). Hence, the observed Ni nanoparticles may be advantageous. Further study is needed to investigate the activity of these nanoparticles and if they will contribute to active TPBs [16]. The Arrhenius-type plots of the total conductivities of NiO/ScSZ samples with different g/n ratios under Ar and O\({}_{2}\) gas flow environments, and under a Ar/5%H\({}_{2}\) gas flow environment, at a 500-700 \({}^{\circ}\)C operating temperature range are shown in Figures 5 and 6, respectively. The conductivities were calculated based on the results of the EIS measurements, wherein the resistance observed can be related to the conductivity with the following equation:  
\[\sigma=\frac{t}{AR} \tag{1}\]  
where the resistance (\(R\)) taken from EIS Nyquist plot can then be converted to conductivity (\(\sigma\)) using the cross-sectional area (\(A\)) and thickness (\(t\)) of the sample pellet. As shown in Figure 5, under O\({}_{2}\) gas flow environment, the samples showed higher total conductivity compared to the Ar gas flow, which is possibly due to the increase in the oxide ion conductivity contribution from ScSZ and/or other defect associations with the NiO phase under the oxidizing atmosphere. Since conductivity is related to the concentration of the mobile oxide ions and its mobility, the concentration may be depleted under pure Ar gas flow by the creation of oxygen vacancies, dictated by the charge balance of Sc\({}^{3+}\) doping into the Zr\({}^{4+}\) cationic site in the ZrO\({}_{2}\) lattice structure. Hence, the calculated activation energy (Ea) under pure Ar gas is higher compared to O\({}_{2}\) gas flow environment. The doping of Sc\({}^{3+}\) on the Zr\({}^{4+}\) lattice site is given in Equation (2) using the Kroger-Vink notation:  
\[Sc_{2}O_{3}\to 2 Sc^{\prime}_{Zr}+V_{\widetilde{O}}+3O^{x}_{O} \tag{2}\]  
Among the g/n ratios, 0.27 showed the highest total conductivity.