## 4 Conclusions  
The present study has shown that the addition of Sb\({}_{2}\)O\({}_{3}\) to 0.99 Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\)-0.01 Bi(Y\({}_{1-x}\)Sb\({}_{x}\))O\({}_{3}\) [PZT-BYS(\(x\))] ceramics (\(0\leq x\leq 0.6\)) has significantly improved their energy-harvesting properties. The comparative study between doping Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\) into the PZT-BYS(\(x\)) revealed the feasibility of both ceramics for energy harvesting when an appropriate sintering condition is maintained. It was observed that doping Sb\({}_{2}\)O\({}_{3}\) into PZT-BYS(\(x\)) while maintaining the oxygen-rich sintering atmosphere had a significant influence on the dielectric and piezoelectric characteristics. All the Sb\({}_{2}\)O\({}_{3}\)-doped PZT-BYS(\(x\)) ceramics could be well sintered to high densities at temperatures between 1150 and 1170 \({}^{\circ}\)C. The XRD analysis of the sintered sample indicated a pure solid solution of PZT-BYS(\(x\)) without any second phases. The microstructures of the sintered samples were uniform and dense and consistent with the measured density. The Curie temperature of \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multicolumn{1}{c}{**Composition**} & \(g_{33}\times 10^{-3}\) & \(d_{33}\times g_{33}\) & \(T_{\rm C}\) (\({}^{6}\)C) & **Ref.** \\  & & **(Vm/N)** & **(10\({}^{-15}\) m\({}^{2}\)/N)** & **T\({}_{\rm C}\) (\({}^{6}\)C)** & **Ref.** \\ \hline
0.9 Pb(Zr\({}_{0.56}\)Ti\({}_{0.44}\))O\({}_{3}\)–0.1 Pb(Zr\({}_{0.83}\)Ni\({}_{0.2}\))\({}_{1/3}\)Nb\({}_{2/3}\)O\({}_{3}\) + 2 mol\% MnO\({}_{2}\) & 83 & 18,456 & -315 & 41 \\
0.65 + yPb(Zr\({}_{0.47}\)Ti\({}_{0.53}\))\({}_{0.35}\)–(0.35 \(-\) y\(\))PM(Ni\({}_{1-x}\)Zr\({}_{0.1}\))\({}_{1/3}\)Nb\({}_{2/3}\)]O\({}_{3}\) & 36 & 20,056 & \(\cdots\) & 42 \\
0.72 Pb(Zr\({}_{0.76}\)Ti\({}_{0.53}\))O\({}_{3}\)–0.28 Pb(Zr\({}_{0.48}\)Ni\({}_{0.58}\))\({}_{1/3}\)Nb\({}_{2/3}\)]O\({}_{3}\) & 35 & 13,051 & \(\cdots\) & 43 \\ Pb\({}_{0.58}\)La\({}_{0.07}\)(NiNi\({}_{0.58}\))(Zr\({}_{0.83}\))\({}_{0.38}\)(Sr\({}_{2}\)Zr\({}_{0.83}\))\({}_{0.38}\)(Sr\({}_{2}\)Zr\({}_{0.83}\))\({}_{0.38}\)(Sr\({}_{0.95}\))O\({}_{3}\) & 36.8 & 16,570 & \(\cdots\) & 16 \\
0.99 Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\)–0.01 BiYO\({}_{3}\)O\({}_{3}\) & 53 & 18,549 & 373 & 13 \\
0.99 Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\)–0.01 Bi(Y\({}_{0.48}\)Sb\({}_{0.1}\))O\({}_{3}\) & 57.4 & 20,075 & 369 & present \\ \hline \hline \end{tabular}
\end{table} 
Table 4: A comparison between the present work and recently reported piezoelectric ceramic materials for energy-harvesting applications. Figure 9: Calculated values of \(g_{33}\) and \(d_{33}\times g_{33}\) of PZT-BYS(\(x\)) ceramics as a function of different Sb\({}_{2}\)O\({}_{3}\) contents. the ceramics was shown to produce a linear reduction with increasing Sb\({}_{2}\)O\({}_{3}\) contents, but it is still high enough to use for high-temperature applications. The observed piezoelectric properties were in agreement with the measured _P-E_ hysteresis loops. A maximum \(d_{33}\) of 370 pC/N at \(x\) = 0.6 moles and a maximum \(k_{\rm P}\) of 66% at \(x\) = 0.1 moles were observed. It was also observed that the \(\varepsilon_{33}\)T (690) sharply decreased at \(x\) = 0.1 while maintaining relatively higher \(d_{33}\) (350 pC/N), which is a highly demanding piezoelectric characteristic for energy-harvesting. The relatively higher \(d_{33}\) and lower \(\varepsilon_{33}\)T at \(x\) = 0.1 resulted in an optimum value of \(g_{33}\) = 57.4 \(\times\) 10\({}^{-3}\) Vm/N and \(d_{33}\)\(\times\)\(g_{33}\) = 20075 \(\times\) 10\({}^{-15}\) m\({}^{2}\)/N, which is high among recently reported work. Therefore, the newly reported ceramic composition of 0.99 Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\)-0.01 Bi[Y\({}_{(1-x)}\)Sb\({}_{x}\)]O\({}_{3}\) could be a promising material for future study to be used in an energy harvester.