## 3 Results and Discussion
### The Piezoelectric and Dielectric Properties of PZT-BYS(\(x\)) Ceramics  
Figure 6a,b shows the effects of Sb\({}_{2}\)O\({}_{3}\) contents on \(d_{33}\), \(k_{\rm p}\), \(\epsilon_{33}\)T and grain size. In addition, the electrical properties of PZT-BYS(\(x\)) samples sintered at their optimum temperature have been listed in Table 2. From Table 2, it is clear that doping Sb\({}_{2}\)O\({}_{3}\) into the PZT-BY increased the \(d_{33}\) and \(k_{\rm p}\) sharply compared to the undoped specimen. This can be explained by factors like the density, grain size and soft effect of Sb\({}_{2}\)O\({}_{3}\). Previously, it was observed that pre-synthesized BiYO\({}_{3}\) acts as a donor  
\begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline
**Composition** & \begin{tabular}{c} **Sintering** \\ **Temp.** (**C**) \\ \end{tabular}  & \begin{tabular}{c} **Grain** \\ **Size (um)** \\ \end{tabular}  & \begin{tabular}{c} \(p\) \\ **(g/cc)** \\ \end{tabular}  & \begin{tabular}{c} \(d_{\rm B}\) \\ **(g/cm)** \\ \end{tabular}  & \(\epsilon_{33}\)T & \(k_{\rm p}\) (**S**) & \begin{tabular}{c} **P\({}_{\rm c}\)** \\ **(u/cm)** \\ \end{tabular}  & \begin{tabular}{c} **E\({}_{\rm C}\) \\ **(g/cm)** \\ \end{tabular}  & \ \begin{tabular}{c} **T\({}_{\rm C}\)** \\ **(g/cm)** \\ \end{tabular}  &
\begin{tabular}{cinto the PZT ceramics and improves the piezoelectric and dielectric properties. In the present work, incorporating Sb\({}_{2}\)O\({}_{3}\) into the PZT ceramic further improved the piezoelectric and dielectric properties because it is possible that the Sb\({}^{3+}\) entered into the A-site and facilitated the domain wall movement. A similar observation was also reported by [PERSON] et al. where they doped Sb\({}^{3+}\) into the Pb\({}^{2+}\) site [20]. Additionally, The Sb\({}_{2}\)O\({}_{3}\)-doped specimen shows higher sintered density (7.96 g/cm\({}^{3}\) at \(x=0.1\)) than the undoped specimen (7.91 g/cm\({}^{3}\) at \(x=0.0\)). As a result, adding Sb\({}_{2}\)O\({}_{3}\) into the PZT improved the \(d_{33}\) and \(k_{\rm p}\) sharply (at \(x=0.1\)) compared to the undoped specimen (at \(x=0.0\)). A detailed explanation of increasing piezoelectric, dielectric and ferroelectric behavior of the Sb\({}_{2}\)O\({}_{3}\)-doped sample will be discussed in the next paragraph. In Figure 6a, it is clear that the \(d_{33}\) and the \(k_{\rm p}\) increase with increasing amount of Sb\({}_{2}\)O\({}_{3}\). The increased density and homogeneous grain size might be a reason for high \(d_{33}\) and \(k_{\rm p}\). The increasing behavior of \(d_{33}\) with the addition of Sb\({}_{2}\)O\({}_{3}\) into PZT was also explained by [PERSON] et al. [14]. In general, donor doping in PZT is expected to increase the \(d_{33}\) and the \(k_{\rm p}\) values, which is a soft effect [25]. In the previous work, it was observed that BiYO\({}_{3}\) acts as a grain growth inhibitor as well as a donor in the vicinity of grains which improve \(d_{33}\) and \(k_{\rm p}\) in the PZT-BY system [13]. In the present case, similar trends of \(d_{33}\) and \(k_{\rm p}\) were also observed. Furthermore, the increasing tendency of \(d_{33}\) can be explained by the presence of second phases, as shown in Figure 1a. It is possible that the second phases of Y\({}_{3}\)Sb\({}_{5}\)O\({}_{12}\), Bi\({}_{2}\)O\({}_{3}\), Y\({}_{2}\)O\({}_{3}\), and BiSbO\({}_{4}\), as shown in Figure 1a, dissociate at the higher sintering temperature. It can be speculated that Bi\({}^{3+}\), Y\({}^{3+}\) and Sb\({}^{3+}\) enter into the Pb\({}^{2+}\) site as donor ions in the PZT system to create A-site vacancies in the lattice. Similarly, a donor doping effect of Sb\({}^{3+}\) was reported by [PERSON] et al. [20]. They studied the structural, dielectric and electrical properties of PZT ceramic extensively to find out the effect of double-doping (La\({}^{3+}\) and Sb\({}^{3+}\)) at the Pb\({}^{2+}\)-site of PZT.