## 3 Results and Discussion  
### Structural and Microstructural Characterization  
Figure 1 presents the X-ray diffraction patterns of (K\({}_{0.44}\)Na\({}_{0.52}\)Li\({}_{0.04}\))(Nb\({}_{0.9-x}\)Ta\({}_{0.1}\)Sb\({}_{x}\))O\({}_{3}\) [KNL\(-\)(N\({}_{0.9-x}\)TS\({}_{x}\))]ceramics for different Sb amounts (\(x\) = 0, 0.02 and 0.04) sintered at 1125 \({}^{\circ}\)C for 2 h. At room temperature, the diffraction patterns within the XRD resolution are consistent with a perovskite structure that is devoid of secondary phases [21,22] (Figure 1a). In addition, Figure 1b shows a zoomed-in area of the XRD pattern in the 26 range 44.5\({}^{\circ}\) to 46.5\({}^{\circ}\) of the KNL\(-\)(N\({}_{0.9-x}\)TS\({}_{x}\))ceramic system. A splitting connected to the coexistence of an orthorhombic symmetry, O, and a tetragonal symmetry, T, may be found in all samples. On KNL\(-\)NTS bulk ceramics, the coexistence of several polymorphs (including the tetragonal and orthorhombic phases) was documented [16]. This fact allows the deconvolution of the perovskite phase's tetragonal symmetry into two Lorentzian peaks, (002)\({}_{\rm T}\) and (200)\({}_{\rm T}\). Additionally, two peaks at 45.2 and 45.7 degrees (20) related to the orthorhombic symmetry are found in these samples. In the same way, a slight shift of the peaks towards higher angles is observed by the Sb effect. The peaks connected to the tetragonal symmetry are more significant in samples with greater Sb amounts. It can be suggested that differences in the ionic radius between Sb\({}^{+5}\) (0.62A) and Nb\({}^{+5}\) (0.69A) produce a distortion of the crystal lattice, with a diminution in the 'a' lattice parameter of the perovskite [23]. However, different effects are produced with the addition of Sb\({}^{+5}\)  
Figure 1: XRD patterns between the 20 range 20 to 70\({}^{\circ}\) (**a**) corresponding to the KNL\(-\)(N\({}_{0.9-x}\)TS\({}_{x}\))sintered at 1125 \({}^{\circ}\)C for 2 h, (**b**) zoomed in on the 20 range of 44.5–46.5\({}^{\circ}\), (**c**) orthorhombic and tetragonal fraction at different Sb amounts. On the one hand, the substitutional addition of Sb\({}^{5+}\) should reduce the cell (due to the smaller ionic radius) displacing the peaks towards higher angles, but on the other hand, the increasing concentration of Sb\({}^{5+}\) generates a structural change modifying the T/O content in the structure. Furthermore, similar results were reported by other researchers showing that small cations in B\(-\)sites facilitate the coexistence of different phases (from rhombohedral-tetragonal to orthorhombic-tetragonal) at room temperature, decreasing the T\({}_{\rm O-T}\) toward room temperature, which can indicate that the T\({}_{\rm O-T}\) was very near to or below room temperature [19; 20]. The composition dependencies of \(V_{T}\) and \(V_{O}\) are shown in Figure 1c to support the previous explanation. A close examination of Figure 1c demonstrates that \(V_{T}\) and \(V_{O}\) are dependent on the Sb\({}^{5+}\) content. \(V_{T}\) rises as \(x\) rises, reaching a maximum value at \(V_{T}\sim\)80% and a T/O ratio close to 4 for \(x=0.04\). Raman spectroscopy was additionally used to evaluate the change in the crystalline structure with composition. The obtained spectra are shown in Figure 2a for samples with different Sb amounts (0.00 to 0.04). Furthermore, a series of main bands located at 250, 560, 615, and 860 cm\({}^{-1}\), products of the vibration modes associated with the KNN and the NbO\({}_{6}\) octahedron, can be observed. These bands are located at \(\upsilon_{5}\), \(\upsilon_{2}\), \(\upsilon_{1}\) and \(\upsilon_{1+5}\) Raman modes, respectively. The practically equilateral octahedral symmetry is found in systems similar to the KNN, and it is associated with the apparition of modes A\({}_{\rm 1g}\) and F\({}_{\rm 2g}\). [24; 25; 26].