**5. The effects of Zr/Ti ratio on the structure, microstructure, and the electrical properties of 0.8Pb(ZryTi1−***y***)O3–0.125Pb(Zn1/3Nb2/3) O3–0.075Pb(Mn1/3Nb2/3)O3 ceramics**

The influence of Zr/Ti ratio on the structure of PZT-PZN-PMnN ceramics has been analyzed through the X-ray diffraction patterns (**Figure 11**). The patterns reveal a pure perovskite phase for all ceramic samples.

As can be seen, the tetragonality of PZT-PZN-PMnN ceramics decreased with increasing Zr/Ti ratio content through the c/a ratio decreases. According to Dixit et al. [46] and Kahoul et al. [47], the morphology of Pb(Zr,Ti)O3 ceramics is strongly dependent on the Zr and Ti content. The content of the rhombohedral phase gradually increases within decreasing the Zr content simultaneously, and the tetragonal phase gradually decreases. The morphological evolution with Zr contents in this work may be attributed to the increase of a rhombohedral phase in these ceramics [46, 47]. This may be because the large Zr+4 (0.86 Å) ions diffuse into the PZT-PZN-PMnN lattice to replace Ti4+ (0.61 Å), resulting in the increase in the lattice constant and a shift in the XRD peak position toward lower 2*θ* values, similar to our recent research [48].

Effects of the contents of Zr/Ti ratio on the microstructure development of the ceramics are shown in **Figure 12**. In general, surface ceramics with large grains and *The Investigation on the Fabrication and Characterization of the Multicomponent Ceramics… DOI: http://dx.doi.org/10.5772/intechopen.93534*

### **Figure 11.**

*X-ray diffraction patterns of ceramics with different Zr/Ti ratio contents: M46 (Zr/Ti = 46/54), M47 (Zr/Ti = 47/53), M48 (Zr/Ti = 48/52), M49 (Zr/Ti = 49/51), M50 (Zr/Ti = 50/50), and M51 (Zr/Ti = 51/49).*

### **Figure 12.**

*Microstructures of samples with the different Zr/Ti ratio contents: MZ46 (Zr/Ti = 46/54), MZ47 (Zr/ Ti = 47/53), MZ48 (Zr/Ti = 48/52), MZ49 (Zr/Ti = 49/51), MZ50 (Zr/Ti = 50/50), and MZ51 (Zr/Ti = 51/49).*

uniform microstructure were obtained in all samples, and the average grain size of samples is increased with the increasing content of Zr/Ti ratio. In conformity with the previous densification results, highly dense samples exhibited high degrees of grain close packing. However, some pores and abnormal grain boundaries were observed in **Figure 12** (MZ50 and MZ51) and the average grain size is reduced.

**Figure 13** shows the temperature dependence of *ε* and tan *δ* of the ceramic samples measured at different frequencies (1 kHz–1 MHz). It can see that with the increase in Zr amount, the *T*m temperature of ceramics decreases as indicated in **Figure 14**. This may explain that the Curie temperature of PbZrO3 ceramics is about 232°C [25], and it is lower than that of PbTiO3 ceramics, 490°C [49, 50]. It is due to the decrease of lattice parameters and bond lengths [46, 47].

In order to determine the piezoelectric properties of ceramics, resonant vibration spectra of the PZT-PZN-PMnN samples were measured at room temperature (**Figure 15**), and from these resonant spectra, the piezoelectric parameters of the samples, such as electromechanical coefficients *k*p, piezoelectric coefficients *d*31, mechanical quality coefficient *Q*m, and dielectric loss tan *δ* were determined (**Figure 16**).

### **Figure 13.**

*Temperature dependence of relative dielectric constant* ε *and dielectric loss tan δ of samples at different frequencies: MZ46 (Zr/Ti = 46/54), MZ47 (Zr/Ti = 47/53), MZ48 (Zr/Ti = 48/52), MZ49 (Zr/Ti = 49/51), MZ50 (Zr/Ti = 50/50), and MZ51 (Zr/Ti = 51/49).*

**Figure 14.** *The Curie temperature* T*m of PZT-PZN-PMnN ceramics with different amounts of Zr/Ti ratio.*

It can be observed that the *k*p, *d*31, *Q* m, and tan *δ* depend on the amount of the Zr/Ti ratio content. The piezoelectric properties of ceramics are markedly improved. The following optimized values were obtained at Zr/Ti = 48/52, *k*p = 0.62, *d*31 = 140 pC N−1, *Q* m = 1112, and tan *δ* = 0.005. This fact can be explained by the increased grain size effect and better modification of microstructure in ceramics [10, 25, 49, 50]. However, with the further increasing the Zr/Ti ratio content, the electrical properties of PZT-PZN-PMnN ceramics are reduced. The cause is due to an abnormal grain boundary, and the average grain size is also reduced, as shown in **Figure 12**.

The *P-E* hysteresis loops of PZT-PZN-PMnN at room temperature are displayed in **Figure 17(a)**, and *P*r and *E*c are presented in **Figure 17(b)**. With the increase in *P*r and the decrease in *E*c, the ferroelectric properties of PZT-PZN-PMnN ceramics improve. With increasing of Zr/Ti ratio content, the value of *P*r increases and reaches the highest value of 34.5 μC/cm<sup>2</sup> ) at the Zr/Ti ratio of 48/52, and then decreases. The coercive field *E*C decreases slightly with the increasing of Zr/Ti ratio content and reaches the smallest value of 9.0 kV/cm at Zr/Ti ratio of 48/52.

*The Investigation on the Fabrication and Characterization of the Multicomponent Ceramics… DOI: http://dx.doi.org/10.5772/intechopen.93534*

### **Figure 15.**

*The spectrum of radial resonance of MZ48 sample (at room temperature).*

**Figure 16.** *The values of* k*p,* d*31,* Q*m, and tan* δ *of the PZT-PZN-PMnN ceramic samples.*

### **Figure 17.**

*(a) Hysteresis loops of samples and (b)* P*r and* E*c as a function of Zr/Ti ratios.*

The effect of temperature on the ferroelectric properties of ceramics was studied by the hysteresis loops of the 0.8Pb(Zr0.48Ti0.52)O3–0.125Pb(Zn1/3Nb2/3) O3–0.075Pb(Mn1/3Nb2/3)O3 sample in the temperature range of 30–280°C

**Figure 18.** *(a) Hysteresis loops and (b) temperature dependence of Pr and EC of MZ48 sample at a different temperature.*

(**Figure 18(a)**). The hysteresis loops of the ceramics exhibited excellent temperature stability due to the broad diffusive phase transition between the nonergodic and ergodic relaxor states that coexisted over a wide temperature range [51]. When the temperature increased from room temperature to 120°C, the remanent polarization and the coercive field increased (**Figure 18(b)**). The reason is when the temperature increases, the oxygen vacancies in the perovskite structure will move and significantly increase the conductivity of the material, which should increase the dielectric loss. However, when the temperature rises above 120°C, the remanent polarization *P*r and the coercive field *E*c decreased (**Figure 18(b)**). Generally, the size of the hysteresis loops depends on the dielectric loss of the material and the metastable macro-domain structure and the immobilizations of the domain walls [52]. Therefore, when the temperature increased, large thermal motion energy caused an increase in bipolar disorder, narrowed the hysteresis loops, and decreased the remanent polarization and the coercive field. In addition, the hysteresis loops showed that the *P*r is nonzero at *T*m but decays to zero at temperatures above *T*m. These results are consistent with the literature [40].
