**4. The effects of Pb(Zr0.47Ti0.53)O3 on the structure, microstructure, and the dielectric properties of** *x***Pb(Zr0.47Ti0.53)O3-(0.925 −** *x***) Pb(Zn1/3Nb2/3)O3-0.075Pb(Mn1/3Nb2/3)O3 ceramics**

Lead-zinc niobate Pb(Zn1/3Nb2/3)O3 (PZN) materials were first synthesized in the 1960s [35, 36]. It is one of the well-known relaxor perovskite ferroelectrics exhibiting a diffused phase transition with a phase transition temperature around 140°C (*T*m) [6, 12]. However, pure perovskite lead-zinc niobate ceramics are relatively difficult to prepare by conventional solid-state reaction method [37]. The addition of other perovskite materials such as PbTiO3, BaTiO3, and PbZr0.47Ti0.53O3 (PZT) is necessary to stabilize the perovskite structure for PZN ceramics [12, 25, 38, 39]. The B-site ions in the PZT perovskite structure (Zr4+, Ti4+) might have been partially substituted by the B-site ions of the relaxor-type PZN structure (Zn2+, Nb5+), which allowed the PZT-PZN solid-solution system to retain the perovskite structure and the high sinterability of lead-based relaxor ceramics [12, 25, 38, 39]. Based on the preparation of pyrochlore-free Pb(Ni1*/*3Nb2*/*3)O3 (PNN), Vittayakorn et al. [40] studied the effects of PZT contents on the dielectric and ferroelectric properties of 0*.*5PNN-(0*.*5 − *x*) PZN-*x*PZT ceramics. The results showed that the dielectric constant (*ε*r), the remanent polarization (*P*r), and Curie temperature (*T*c) increase with the increase in PZT content. With the combination of the preeminent properties between PZT, PZN, and PMnN, the PZT-PZN solid-solution systems hope to achieve the prominent properties of normal ferroelectric PZT and relaxor ferroelectric PZN and PMnN, which could exhibit better piezoelectric and dielectric properties simultaneously. In this section, in order to improve electrical properties, we have prepared *x*PZT- (0.925 − *x*)PZN-0.075PMnN ceramics with the content of PZT from 0.65 to 0.90. The *x*Pb(ZryTi(1−*y*)O3-(0.925 − *x*)Pb(Zn1/3Nb2/3)O3–0.075Pb(Mn1/3Nb2/3)O3 ceramic samples have been fabricated by the B-site oxide mixing technique as described in Section 2.

**Figure 5** shows XRD patterns of the PZT-PZN-PMnN ceramics at various contents of PZT. As observed, all ceramics have pure perovskite phase with dominantly tetragonal structure. The lattice parameters (*a*, *c*) of the samples have been evacuated from the (002) and (200) peaks of diffraction patterns, which are shown in the inset of **Figure 5**. When PZT content increases, the tetragonality *c*/*a* ratio increases. According to the PbZrO3-PbTiO3 phase diagram, Pb(Zr0.47Ti0.53)O3 is the tetragonal phase (space group P4mm) near the morphotropic phase boundary region at room temperature (RT) [41, 42]. While Pb(Mn1*/*3Nb2*/*3)O3 is a cubic structure and the PZN composition was determined to be the rhombohedral (space group R3m) [36, 38]. Therefore, with increasing the molar fraction of PZT, the crystal symmetry of the PZT-PZN-PMnN should change due to the tetragonal distortions of PZT [6, 25, 40]. In order to determine what chemical composition of the PZT-PZN-PMnN ceramic changes during sintering, the EDS analysis is performed and is shown in **Figure 6**. The presence of lithium (Li) is not plotted here because its atomic number is low and the mass percentage is too small [43]. **Table 1** also showed the comparison in the mass of Pb, Zr, Ti, Nb, Zn, and Mn elements between before and after sintering of the PZT-PZN-PMnN ceramics. It is quite clear that the chemical composition of the synthesized ceramic obtained by EDS analysis can roughly accord with

**Figure 5.** *XRD patterns of PZT-PZN-PMnN ceramics at various contents of PZT.*

**Figure 6.** *EDS spectrum of 0.8PZT-0.125PZN-0.075PMnN ceramics.*

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


**Table 1.**

*The chemical composition of the PZT-PZN-PMnN ceramics.*

**Figure 7.** *Surface morphologies observed by the SEM of PZT-PZN-PMnN ceramics at various contents of PZT.*

the general formula of the material without Pb. The reason could be explained by the evaporation of PbO during sintering [6, 25, 31]. Therefore, it is necessary to add excess 5 wt% PbO to compensate for lead loss during sintering.

**Figure 7** shows microstructures of the PZT-PZN-PMnN ceramics at various contents of PZT. The average grain size of these samples is increased with the increase of PZT content in **Table 2**. On the other hand, the average grain size is reduced when x increases above 0.8. These results are obviously consistent with the change in the density of PZT content of PZT-PZN-PMnN ceramics, as shown in **Table 2**.


**Table 2.**

*The average grain size of PZT-PZN-PMnN ceramics.*

**Table 2** shows the density of the PZT-PZN-PMnN ceramics as a function of the PZT content. With the increase of PZT content up to 0.8, the mass density of PZT-PZN-PMnN ceramics increases. It achieves a maximum value (*ρ* = 7.81 g/cm3 , 96% of the theoretical density in which the theoretical density of ceramic is calculated using Eq. (1):

$$
\rho = \frac{nA}{V\_c N\_A} \tag{1}
$$

where n = number of atoms associated with each unit cell in ABO3, A = atomic weight, VC = volume of the unit cell in ABO3, and NA = Avogadro's number.

 This is explained by the content of PZT was added to the ceramic system is less than 0.8 mol, a large number of pores were present, indicating insufficient densification of the sample (**Figure 7**: some SEM for M70, M90 are missing and M75 is not good). As the PZT content increases, the ceramics became denser, and the sample was almost fully dense at a PZT content of 0.8 mol.

The PZT content dependence of the dielectric constant (*ε*r), dielectric loss (tan *δ*), and mass density (ρ) of the PZT-PZN-PMnN ceramics at 1 kHz and RT is illustrated in **Figure 8**. It can be seen that dielectric properties are strongly influenced by the composition of the ceramics. When the content of PZT increases from 0.65 to 0.8 mol, values of *ε*r increase and reach to the maximum of 1230 at 0.8 mol of PZT. Then, these rapidly decrease with increasing *x*, while tan *δ* decreases with increasing PZT content. The minimum tan *δ* of 0.005 is obtained at *x* = 0.8 and then increased. It could be explained by the combination of a large and homogeneous grain size and the highest densification for the composition of 0.8PZT-0.125PZN-0.075PMnN ceramic [22].

In order to characterize the dielectric loss of all samples, the measurement of dielectric constant dependent on temperature is carried out at 1 kHz, as shown in **Figure 8**. With increasing PZT content, the dielectric constant peak increases and becomes sharpened. Hence, the material properties change from relaxor ferroelectricity to normal ferroelectricity. The permittivity and the maximum temperature (*T*m) of the ceramics are shown in **Figure 9**. It shows that the *T*<sup>m</sup> increases with increasing PZT content and is in the range of 206–275°C. There is a difference between the phase transformation temperatures of PZN (*T*m ~ 140°C) [36, 38, 40] and PZT (*T*C ~ 390°C) [25, 35], so it is significant to study the dependence of phase transition temperature of the PZT-PZN-PMnN ceramics on PZT content [40]. When the temperature is higher than *T*m, the function *ε*(*T*) is out of order the Curie-Weiss law in the normal ferroelectric materials. The fact the relationship between dielectric constant (*ε*) and temperature (*T*) above *T*m can be complied by the modified Curie-Weiss law for analyzing of experimental data [44] is shown as follows:

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

**Figure 8.** *Temperature dependence of the dielectric constant and dielectric loss tan δ at 1 kHz of samples.*

**Figure 9.** *The plot of ln(1/ε – 1/εm) versus ln(T-Tm) of PZT-PZN-PMnN ceramics at 1KHz.*

$$\frac{\mathbf{a}}{\mathcal{E}} - \frac{\mathbf{a}}{\mathcal{E}\_{\text{max}}} = \frac{\left(T - T\_m\right)^{\gamma}}{\mathcal{C}^{\prime}} \tag{2}$$

where *C* is the modified Curie–Weiss constant and *γ* is the diffuseness exponent, which changes from 1 to 2 for normal ferroelectrics to fully disorder relaxor ferroelectrics, respectively [44].

The slopes of the fitting curves (**Figure 9**) are used to determine the *γ* value of *x*PZT-(0.925 − *x*)PZN-0.075PMnN ceramics at 1 kHz. As can be seen in **Figure 9**, the *γ* changes from 1.70 to 1.88. Thus, it is indicated that the transitions are of a diffuse type and the ceramics are highly disordered.

To analyze the frequency dependence of *T*m, it is necessary to use Vogel-Fulcher law [6, 45]:

$$F = f\_o \exp\left(-T\_o \,/\left(T - T\_f\right)\right) \tag{3}$$

$$Ln\left(f\right) = f\_o - T\_o \left(T\_{\nu u} - T\_f\right) \tag{4}$$

**Figure 10.** *The plot of ln(*f*) versus* T*m as a function of the measured frequency of PZT-PZN-PMnN.*


### **Table 3.**

*The value of fitting parameters to Vogel-Fulcher relationship.*

where *T*f is the freezing temperature, *E*a is the activation energy for polarization fluctuation of a polar nanoregion, *f*o is a characteristic frequency or Debye frequency, and *k*B is the Boltzmann constant = 1.38 × 1023 J/K, and *T*o = *E*a/*k*B. **Figure 10** shows the plot of ln(*f*) versus *T*m as a function of the measured frequency of PZT-PZN-PMnN. The symbols are the experimental points, and the line is the corresponding fitting to the Vogel-Fulcher relationship as listed in **Table 3**.
