## 3 Results and Discussion
At 700 \({}^{\circ}\)C, the total conductivity of the 0.27 g/n sample was 4.5 \(\times\) 10\({}^{-3}\) S/cm and 1.2 \(\times\) 10\({}^{-2}\) S/cm under Ar and O\({}_{2}\) gas flow environments, respectively. The calculated activation energies are 1.23 eV, 1.10 eV, and 1.16 eV under Ar and 0.57 eV, 0.40 eV, and 0.51 eV under O\({}_{2}\) gas flow for g/n ratios of 0.27, 0.54, and 1.1, respectively. Figure 4: SEM images of reduced Ni/ScSZ (g/n = 0.27) at high magnifications with 20,000\(\times\) (top) and 50,000\(\times\) (bottom). Figure 5: Arrhenius-type plot of the total conductivity at intermediate temperatures for NiO/ScSZ with different g/n ratios under Ar and O\({}_{2}\) gas flow environment from 500 \({}^{\circ}\)C to 700 \({}^{\circ}\)C.  
Using the 2-electrode configuration in the EIS measurements, the calculated total conductivities of the reduced samples in Arrhenius-type plot are shown in Figure 1:0 The g/n ratio of 0.27 has almost twice the conductivity compared to the other samples. The total conductivities at 700 \({}^{\circ}\)C are 7.66 \(\times\) 10\({}^{-2}\) S/cm, 4.03 \(\times\) 10\({}^{-2}\) S/cm, and 3.27 \(\times\) 10\({}^{-2}\) S/cm for 0.27, 0.54, and 1.1 g/n ratios, respectively. The reduced Ni/ScSZ samples has higher total conductivity than NiO/ScSZ. Although, there are only few or no reports for the total conductivity of Ni/ Zr\({}_{0.84}\)Sc\({}_{0.16}\)O\({}_{1.92}\) with 1:1 wt % composition, the conductivity is lower if compared to the reported Ni/YSZ cermet, which is about 300-1000 S/cm [17,18]. This may be due to the limitation of the EIS measurement employed in this study compared to the four-point probe direct current (DC) technique. With the same EIS measurement, another study reported an electrical conductivity of 1.58 S/cm at 900 \({}^{\circ}\)C for Ni/YSZ [19]. In addition, the lower total conductivity observed in this study for Ni/ScSZ may be due to the more porous nature of our reduced sample. For thin film of Ni/10 ScSZ with 40 vol % Ni, an electrical conductivity of 300 S/cm at 700 \({}^{\circ}\)C was reported using the four-point probe DC technique [11]. Hence, our future study will involve further characterization of Ni/ScSZ using the four-point probe DC technique and to investigate the ionic and electronic contributions to the total conductivity. In order to investigate the structural change in ScSZ in the Ni/ScSZ cathode composition, in-situ high-temperature XRD was conducted. Figure 7 shows the in-situ XRD stack patterns of the reduced Ni/ScSZ sample for the 0.27 g/n ratio under a A5/5%H\({}_{2}\) gas flow. The pattern revealed that ScSZ with the Zr\({}_{0.84}\)Sc\({}_{0.16}\)O\({}_{1.92}\) composition can retain its cubic phase structure as observed from the XRD results when subjected to 500-800 \({}^{\circ}\)C operating temperatures. Figure 7b shows the 111 peaks, and the pattern suggested a cubic phase retention at these intermediate temperatures. There is a remnant formation of NiO due to possible oxidation of the reduced Ni inside the in-situ high temperature XRD sample chamber apparatus due to remaining oxygen inside the apparatus that was not vacuumed. Figure 8 shows the calculated lattice constant change in ScSZ and Ni, which revealed a slight increase in the cubic lattice constant at 500-800 \({}^{\circ}\)C. At room temperature, the lattice constant calculated is 5.09 A and 3.53 A for ScSZ and Ni, respectively. Figure 1:1 Arrhenius-type plot of the total conductivity at intermediate temperatures for the reduced Ni/ScSZ with different g/n ratios under Ar/5%H\({}_{2}\) gas flow environment from 500 \({}^{\circ}\)C to 700 \({}^{\circ}\)C.