## 3 Results and Discussion  
X-ray Diffraction (XRD) Analysis of Pre-Synthesized PZT and Bi[Y\({}_{(1-x)}\)Sb\({}_{x}\)]O\({}_{3}\)  
Figure 1a,b shows the X-ray diffraction (XRD) patterns of pre-synthesized Sb\({}_{2}\)O\({}_{3}\)-doped Bi[Y\({}_{(1-x)}\)Sb\({}_{x}\)]O\({}_{3}\) [BYS(\(x\))] (where \(x\) = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6) and Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\) [PZT], respectively. For clarity, only Sb\({}_{2}\)O\({}_{3}\)-doped BYS(\(x\)) is presented here. The reaction mixture of BYS(\(x\)) was characterized by thermogravimetry and differential scanning calorimetry (TG-DSC) to locate the formation temperature. Based on the TG-DSC analysis, undoped BiYO\({}_{3}\) (BY) and PZT was calcined at 850 \({}^{\circ}\)C, whereas both Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\)-doped BY was calcined at 800 \({}^{\circ}\)C for 2 h. In Figure 1a it can be seen that the major phase formed for the BYS(\(x\)) could be related only to the diffraction peak given for BiYO\({}_{3}\) (JCPDS No. 271047). However, a tiny peak of Y\({}_{3}\)Sb\({}_{5}\)O\({}_{12}\) [JCPDS No. 0430160], Bi\({}_{2}\)O\({}_{3}\) [JCPDS No. 0270052], Y\({}_{2}\)O\({}_{3}\) [JCPDS No. 0431036], and BiSbO\({}_{4}\) [JCPDS No. 0480469] was observed in the XRD patterns. Moreover, it can be seen that the intensity and the number of second phases increase with increasing Sb\({}_{2}\)O\({}_{3}\) content. Therefore, the XRD studies indicate that the solubility of Sb\({}_{2}\)O\({}_{3}\) in BY is limited to a certain range. According to [PERSON]'s effective radius [23], Y\({}^{3+}\) and Sb\({}^{3+}\) with a coordination number of six have radii of 0.90 and 0.76 A, respectively. The difference in radii  
between Y\({}^{3+}\) and Sb\({}^{3+}\) ions is greater than 15%. Therefore, it is not easy for Sb\({}^{3+}\) to enter into Y\({}^{3+}\), and the solubility of Sb\({}^{3+}\) in the system would be limited. On the other hand, the calcined PZT powder was fully stabilized to the perovskite structure (JCPDS No. 01-070-4264) without any second phases. Comparative Study of Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\) Doping on the PZT-BY System  
0.99 Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\)-0.01 Bi[Y\({}_{(1-x)}\)Sb\({}_{x}\)]O\({}_{3}\) (abbreviated as PZT-BYS(\(x\)) from now on, where \(x\) = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 moles) ceramics were sintered in air and an O\({}_{2}\)-rich atmosphere to investigate the Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\)-doping effects on the microstructure and electrical properties. Figure 2 shows the microstructure for the fracture surfaces of Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\)-doped PZT-BYS(0.1) ceramic sintered at 1170 \({}^{\circ}\)C in different sintering atmospheres. In addition, the piezoelectric, dielectric, ferroelectric and energy-harvesting parameters of same specimens have been listed in Table 1. From Table 1, it is clear that the piezoelectric properties of Sb\({}_{2}\)O\({}_{5}\)-doped specimens sintered in an air atmosphere and Sb\({}_{2}\)O\({}_{3}\)-doped specimens sintered in an O\({}_{2}\)-rich atmosphere show higher values than the Sb\({}_{2}\)O\({}_{3}\)-doped specimen sintered in air. It may be considered that the presence of oxygen during sintering reduced the porosity and resulted in dense microstructures. Therefore, among other reasons like pre-synthesis, doping, etc., sintering in an oxygen-rich atmosphere is an essential factor for relatively higher piezoelectric properties as well as higher FOM. Figure 1: X-ray diffraction (XRD) patterns of (**a**) Sb\({}_{2}\)O\({}_{3}\)-doped Bi[Y\({}_{1-x}\)Sb\({}_{x}\)]O\({}_{3}\) and (**b**) Pb(Zr\({}_{0.53}\)Ti\({}_{0.47}\))O\({}_{3}\) calcined at different temperatures. Figure 2: SEM (Scanning Electron Microscope) images of the fracture surface of Sb\({}_{2}\)O\({}_{3}\) and Sb\({}_{2}\)O\({}_{5}\)-doped PZT–BYS(0.1) ceramics sintered in different atmospheres (sintered temperature 1170 \({}^{\circ}\)C).