## 3 Results  
Figure 3 shows the X-ray diffraction pattern of the sintered specimens of LSM_F and LSM_K. For the XRD patterns of LSM_F and LSM_K in Figure 3, all peaks were indexed to the La\({}_{0.8}\)Sr\({}_{0.2}\)MnO\({}_{3}\) (LSM) perovskite structure, and no secondary phase was observed. Both LSM_F and LSM_K had the same crystal structure as La\({}_{0.8}\)Sr\({}_{0.2}\)MnO\({}_{3}\) (ICSD 98-005 \begin{table}
\begin{tabular}{c c} \hline
**Variables** & **Dimension** \\ \hline Width (\(w\)) & 3 mm \\ \hline Sample thickness (\(t\)) & 3, 4, 5 mm \\ \hline Spacing between the measurement terminals (\(L\)) & 10, 20 mm \\ \hline Diameter of lead wire (\(\phi\)) & 0.25, 0.50 mm \\ \hline Applied current (\(l\)) & 10, 50, 100 mA \\ \hline \end{tabular}
\end{table} 
Table 1: Experiment variables of DC 4-point method. Figure 2: Schematic diagram of specimen. 1655), with the R-3m hexagonal structure. Figure 4a,b shows the surface morphology of the sintered body. Both specimens had a density and porosity of about 6.4g/cm\({}^{3}\) and 0.09%, respectively. The grain sizes were calculated as 3.29 \(\upmu\)m for LSM_K and 2.74 \(\upmu\)m for LSM_F, according to the Scherrer equation, which corresponded to SEM image. Therefore, it is expected that the difference between the measured values for the two samples will be minimized. Factors that can affect the DC 4-point measurement method are the shape of the specimen, the distribution of defects within the specimen, the contact between the lead wire and the specimen, and the offset of the measuring device, having excluded the characteristics related to the crystal structure and microstructure of the sample. Figure 4: Surface morphology of sintered sample: **(a)** LSM-F and **(b)** LSM-K.  
Figure 3: XRD patterns of LSM powders. The effect of the spacing between the lead wires on the conductivity was evaluated, as shown in Figure 5. The conductivity of each specimen with spacings of 1 cm and 2 cm were calculated after fixing the specimen thickness (5 mm), lead wire diameter (0.50 mm), and applied current (50 mA). Both specimens showed a value of approximately 200 S/cm at 900 \({}^{\circ}\)C, which is similar to that of LSM, as shown in Table 2. In the case of LSM_F, the average and standard deviation value at 900 \({}^{\circ}\)C, which is the operating temperature of LSM, was 187.34 \(\pm\) 20.31 S/cm for the 1 cm electrode spacing and 210.54 \(\pm\) 11.28 S/cm for the 2 cm electrode spacing. For LSM_K, the average and standard deviation value was 201.97 \(\pm\) 13.74 S/cm at 1 cm and 204.85 \(\pm\) 8.00 S/cm at 2 cm, and both specimens had a smaller standard deviation of conductivity at 2 cm. It is considered that a wider spacing of the lead wires is advantageous for more evenly included defects such as grain boundaries and pores, which are randomly distributed in the specimen. To evaluate the effect of the contact between the specimen and the lead wire, the conductivity of each specimen according to the diameter of the lead wire was determined, as shown in Figure 6, where the specimen thickness (5 mm), the lead wire spacing (2 cm), and the applied current (50 mA) were fixed. When the thickness of the lead wire in LSM_F was 0.50 mm, the average and standard deviation value was 210.54 \(\pm\) 11.28 S/cm, and for a thickness of 0.25 mm, the average and standard deviation value was 207.86 \(\pm\) 12.97 S/cm. For both specimens, the standard deviation of the conductivity was smaller for the lead wire thickness of 0.50 mm. When the lead wire is thick, there is a smaller deviation because the lead wire of 0.50 mm can make more stable contact with the sample than the 0.25 mm counterpart.