## 3 Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Additives** & **Sintering Condition (\(\mathbf{\
abla}^{C}\)/ \(\mathbf{h}\))** & **Sintered Density (g/cm)** & **\(\mathbf{\
abla}_{\mathbf{m}}\) (\(\mathbf{\
abla}^{C}\))** & **K (25 °C)** & **tan(25 °C)** & **-55 °C** & **200 °C** & **-55 °C** & **200 °C** \\ \hline
1.0 mol\% Ta\(\mathrm{O}_{5}\) & 1215/2 & 5.82 & 145 & 1788 & 3.6\% & -38.8 & 2.1 & 2.6 \(\times 10^{12}\) & 1.3 \(\times 10^{11}\) \\
1.5 mol\% Ta\(\mathrm{O}_{5}\) & 1215/2 & 5.81 & 150 & 1800 & 2.3\% & -16.1 & -6.4 & 3.5 \(\times 10^{12}\) & 8.2 \(\times 10^{10}\) \\
2.0 mol\% Ta\(\mathrm{O}_{5}\) & 1215/2 & 5.79 & 180 & 1386 & 1.8\% & -13.3 & 5.2 & 2.8 \(\times 10^{10}\) & 1.5 \(\times 10^{10}\) \\
1.0 mol\% Nb\(\mathrm{O}_{5}\) & 1215/2 & 5.79 & 140 & 1471 & 3.9\% & -37.7 & 15.7 & 9.0 \(\times 10^{12}\) & 9.1 \(\times 10^{10}\) \\
1.5 mol\% Nb\(\mathrm{O}_{5}\) & 1215/2 & 5.77 & 140 & 1790 & 3.1\% & -18.4 & -16.5 & 6.2 \(\times 10^{12}\) & 5.5 \(\times 10^{10}\) \\
2.0 mol\% Nb\(\mathrm{O}_{5}\) & 1215/2 & 5.74 & 140 & 1865 & 1.4\% & -9.4 & -19.8 & 7.8 \(\times 10^{12}\) & 5.1 \(\times 10^{10}\) \\ \hline \hline \end{tabular}
* * Resistivity of the samples was measured at a DC voltage of 500 V.  
\end{table} 
Table 2: Dielectric properties of 0.9 BaTiO\(\sim\)0.1(Bi\({}_{0.5}\)Na\({}_{0.3}\))TiO\({}_{3}\) ceramic with various amounts of Ta\(\mathrm{O}\)s and Nb\(\mathrm{O}\)s at their maximum sintered densities. Figure 5: **(a)** Temperature coefficients of capacitance and **(b)** dielectric losses _versus_ temperature of 0.9 BaTiO\(\sim\)0.1(Bi\({}_{0.5}\)Na\({}_{0.5}\))TiO\({}_{3}\) ceramics with addition of various amounts of Nb\(\mathrm{O}\)s sintered at 1215 °C (measured frequency = 1 kHz; heating rate = 2 °C/min; applied voltage = 1 V). The TCCs of the 0.9 BaTiO\({}_{3}\)-0.1(Bi\({}_{0.5}\)Na\({}_{0.5}\))TiO\({}_{3}\) ceramic with 1.0 mol% Ta\({}_{2}\)O\({}_{5}\) at \(-\)55 and 200 \({}^{\circ}\)C were \(-\)38.8% and 2.1%, respectively, which failed to meet the EIA X9R specifications because of the large variation of capacitance between the hot and cold ends (See Figures 4a and 5a). As the Ta\({}_{2}\)O\({}_{5}\) dopant content in the sintered ceramic increased, the capacitance variation at both \(-\)55 \({}^{\circ}\)C and 200 \({}^{\circ}\)C became flattened. The TCCs of the sintered ceramics became X9R-qualified with 2.0 mol% Ta\({}_{2}\)O\({}_{5}\). The TCCs at \(-\)55 \({}^{\circ}\)C and 200 \({}^{\circ}\)C for the sintered ceramics with 1.5 and 2.0 mol% Ta\({}_{2}\)O\({}_{5}\) were, respectively, \(-\)16.1% and \(-\)6.4% and \(-\)1.3% and 5.2%. The dielectric constant of the 0.9 BaTiO\({}_{3}\)-0.1(Bi\({}_{0.5}\)Na\({}_{0.5}\))TiO\({}_{3}\) ceramic tended to decrease with the Ta\({}_{2}\)O\({}_{5}\) content and appeared to be 1788, 1800, and 1386 for 1.0, 1.5 and 2.0 mol% Ta\({}_{2}\)O\({}_{5}\), respectively. However, the dielectric constant increased from 1471 to 1790 and 1865 as the Nb\({}_{2}\)O\({}_{5}\) content rose from 1.0 to 1.5 and 2.0 mol%, respectively. Apparently, the dielectric constant increased with the addition of Nb\({}_{2}\)O\({}_{5}\) dopant, even though the differences in their microstructures, such as grain size and porosity, seemed to be trivial. Capacitors for high-temperature applications must possess a low dielectric loss at both room and high temperatures to prevent overheating and failure. As shown in Figures 4b and 5b, all samples revealed a similar trend in their dielectric-loss curves. The dielectric losses of the sintered 0.9 BaTiO\({}_{3}\)-0.1(Bi\({}_{0.5}\)Na\({}_{0.5}\))TiO\({}_{3}\) ceramics with Ta\({}_{2}\)O\({}_{5}\) and Nb\({}_{2}\)O\({}_{5}\) continued to drop with the measurement temperature. For instance, the dielectric loss of the sintered ceramic with 2.0 mol% Ta\({}_{2}\)Os was 3.3%, 1.8%, and 1.7% at temperatures of \(-\)55, 25, and 200 \({}^{\circ}\)C, respectively.