## 3 Results and Discussion  
Three different samples of 50 wt % NiO and 50 wt % Zr\({}_{0.84}\)Sc\({}_{0.16}\)O\({}_{2-8}\) compositions using different glycine-to-nitrate ratios were synthesized via a modified single-step glycine-nitrate combustion method. In this study, the composite powder of NiO and ScSZ was synthesized using a single-step combustion method wherein the precursor reagents of these two phases, NiO and ScSZ, were mixed in a glassware, in contrast to our previous work, using a double combustion method wherein one phase was GNP-synthesized first before mixing and combusting the second phase [13]. This modified single-step preparation using simple and readily available oxides will be advantageous in the facile preparation of this composite electrode material. In order to study the resulting properties of the prepared samples using this single-step approach, the structure, morphology, and conductivity were investigated. Figure 1 shows the XRD stack patterns for the 0.27 g/n ratio (Figure 1a), 0.54 g/n ratio (Figure 1b), and 1.1 g/n ratio (Figure 1c). For the as-combusted samples, the observed peaks and phases and their relative intensity varied with different g/n ratios. As the g/n ratio increases, the formation of Ni phase increases and the formation of NiO decreases. The observed formation of monoclinic ZrO\({}_{2}\) (m-ZrO\({}_{2}\)) is also the main phase for the smallest g/n ratio compared with the already-formed ScSZ phase for the higher g/n ratio. For the as-sintered samples in all g/n ratios, the phases observed in the XRD pattern were indexed to both cubic phases of NiO (PDF 00-047-1049, a = 4.177 A) and Zr\({}_{0.85}\)Sc\({}_{0.2}\)O\({}_{1.9}\) (PDF 01-089-5485, a = 5.091 A). The calculated lattice parameters for sintered samples of NiO and Zr\({}_{0.84}\)Sc\({}_{0.16}\)O\({}_{1.92}\) are 4.186 A, 4.184 A, and 4.1799 A, and 5.094 A, 5.093 A, and 5.090 A for g/n ratio of 0.27, 0.54, and 1.1, respectively. Compared to the YSZ with a lattice parameter of 5.141 A (PDF 01-083-9463), the lattice parameter of ScSZ is smaller due to a smaller ionic radius of Sc (0.885 A) compared to Y\({}^{3+}\) (1.1 A) into the Zr\({}^{4+}\) (0.92 A) lattice site [13; 15]. The room temperature XRD patterns of the reduced samples are shown in the topmost pattern in Figure 1a-c. It can be observed that the NiO peaks completely disappear with the formation of the metallic Ni phase. The observed Ni phase can be indexed to cubic Ni (PDF 00-004-0850) with a lattice parameter of 3.529 A, 3.529 A, and 3.527 A for g/n ratios of 0.27, 0.54, and 1.1, respectively. Figure 2 reveals the porous microstructures of the as-sintered bulk pellets of NiO/ScSZ (Figure 2a-c) and reduced Ni/ScSZ (Figure 2e,f) at all g/n ratios. It can be observed that the smallest g/n ratio is denser compared with the other two g/n ratios for the as-sintered composites. Upon reduction of these samples to obtain the Ni/ScSZ, the dense and agglomerated particles then revealed a more porous channel or separation in between the grains due to volume reduction and shrinkage when oxygen is released upon reduction of NiO to Ni. From the observed results, the 0.27 g/n ratio showed a more desirable homogeneous porous morphology compared with the other prepared samples. In order to investigate the morphology and composition of the unreduced NiO/ScSZ and the reduced Ni/ScSZ with a 0.27 g/n ratio sample, EDS elemental mapping was performed and the results are shown in Figure 3. As shown in the figure, the NiO and ScSZ ceramics are well mixed in a micron-range distance throughout the sample. The NiO phase is also about 1 micron in size. For the reduced Ni/ScSZ EDS mapping, we observed that there is agglomeration of Ni in the map, which is situated in the vicinity of the connected grains of ScSZ. Figure 1: X-ray diffraction (XRD) stack patterns of the as-combusted, as-sanclined, as-sintered NiO/ScSZ, and as-reduced Ni/ScSZ bulk pellets for g/n ratios of (**a**) 0.27, (**b**) 0.54, and (**c**) 1.1.