*2.2.5 Conclusions for pseudo tungsten-bronze*

*Electromagnetic Materials and Devices*

in **Figure 11(b)**. The internal strain comes from the fluctuation of *d*-spacing of the

*Internal strain η values obtained from the slope of equation βcosθ = r/t + 2ηsinθ as a function of sinθ for x = 0.3,* 

*0.5, 2/3 and 0.7 (a) and strain η (d-spacing) as a function of composition x (b).*

GHz in the

GHz in the La system as

lattice broadening the full width at half maximum (FWHM) [20, 21, 56]. The *Qf* value at the special point *x* = 2/3 shows the highest of 10.5 × 103

*Microwave dielectric properties as a function of ionic radius of R ion.*

GHz in the Nd system and 2.0 × 103

depicted in **Figure 8(a)** [20, 21, 56]. The *Qf* values reducing in the order of Sm, Nd, Pr and La are depending on the ionic radius relating size difference between Ba and *R* [57], and that of La is deviating from the *Qf* line through the Sm, Nd and Pr as shown in **Figure 12**. If the sizes are similar, the crystal structure should become perovskite structure. In the case of Sm, the difference is maximum which introduces the stability of the crystal structure. The size of La ion is similar to Ba, so the structure might be

On the microwave dielectrics, high *Q* has been brought by a high potential material, which has an over-well-proportional rigid crystal structure with symmetry

**12**

Sm system, 10.0 × 103

**Figure 12.**

**Figure 11.**

unstable to be low *Qf*.

*2.2.4 Symmetry and ordering for Q*


#### **2.3 Complex perovskites**

There are many kinds of complex perovskites such as 1:1, 1:2 and 1:3 type in *B*-site and 1:1 type in *A*-sites [21]. In this chapter, 1:2 type complex perovskite compounds *A*2+(*B*2+ 1/3*B*5+ 2/3)O3 are presented such as Ba(Zn1/3Ta2/3)O3 (BZT), Ba(Mg1/3Ta2/3)O3 (BMT) and Ba(Zn1/3Nb2/3)O3 (BZN). These complex perovskite compounds have order-disorder phase transitions (**Figure 13(a)** and **(b)**) [58]. The ordered phase that appears at low temperatures is a trigonal (rhombohedral) structure of space group *P*¯ <sup>3</sup>*m*1 (No. 164), and the disordered phase appearing at high temperatures is a high symmetry cubic structure of *Pm*¯ <sup>3</sup>*m* (No. 221), as shown

**Figure 13.**

*Complex perovskite crystal structure composed by Mg/TaO6 octahedra located between BaO3 closed packing layer, showing relationship between cubic and trigonal crystal lattice. Perspective figure (a) and (110) plane (b).*

in **Figure 13** [21]. In the ordered form of BMT, Mg2+ and Ta5+-ions located among the adjacent packing layers of BaO3 are ordering as -Mg-Ta-Ta-Mg-Ta-Ta-Mg-, as shown in **Figure 13**. On the other hand, in the disordered form, Mg2+ and Ta5+-ions occupy *B*-sites statistically.

## *2.3.1 Introduction*

Kawashima et al. [14] presented that ordering brings a high *Q* based on BMT with long duration sintering, which showed high *Qf* and ordering. This has previously been believed to be the case because long duration sintering samples generally show high *Qf* and ordering. However, some examples have arisen that contradict this relation, such as BMT-Ba(Co1/3Ta2/3)O3 [59], BMT-BaZrO3 [60], BMT-BaSnO3 [61] and BZT-(SrBa)(Ga1/2Ta1/2)O3 [62]. Koga et al. [23–26] presented the relationship between high *Qf* and the ordering ratio as determined by the Rietveld method, the high *Qf* samples with disordered structure synthesised by spark plasma sintering (SPS) [63] and the effects of annealing of disordered BZN with an orderdisorder transition point of 1350°C [26]. HRTEM and Rietveld studies confirmed the ordering and disordering of BZN samples [64]. Partial ternary phase diagrams such as BaO-ZnO-Ta2O5, BaO-MgO-Ta2O5 and BaO-ZnO-Nb2O5 were studied on the composition with high *Qf* that deviated from the stoichiometric composition of BZT/BMT/BZN by Kugimiya et al. [22, 27], Koga et al. [24, 26] and Kolodiazhnyi [29]. Kugimiya pointed out that the solid solutions with high density and high *Qf* located on the tie-line BMT-Ba5Ta4O15, which have completed the ideal chemical formula without oxygen defects. It is one of the conditions for high *Q* that the high compositional density brings high *Qf*.

#### *2.3.2 Origin of high Q for microwave complex perovskite*

In this section, it is explained that ordering has no relation with *Qf* based on the following three sets presented by Koga et al. [23, 25, 26, 63].

#### *2.3.2.1 Ordering ratio and Qf*

The ordering of BZT was observed on the samples with high *Qf* sintered at 1350°C [23] over 80 h. **Figure 14** presents the XRPD patterns (**a**) with super lattice lines (asterisked), and the high angle diffraction patterns (**b**) which depicts splitting of 420 cubic diffraction peak into two peaks, namely 226 and 422 in the trigonal system. These data are consistent with the report by Kawashima et al. [14].

Koga et al. investigated the amount of BZT ceramic as ordering ratio by the Rietveld method [23], which is shown in **Figure 15(a)**. The ordering ratio saturates at about 80%, but the *Qf* values increase up to 100 × 103 GHz. This shows that the effect of ordering on the *Qf* is not so significant. However, the *Qf* values are affected by density and grain size as shown in **Figure 15(b)** and **(c)**, respectively [15, 23].

#### *2.3.2.2 BZN with a clear order-disorder transition*

Many complex perovskites such as BMT and BZT have the order-disorder phase transition at high temperature, and the order-disorder transition is not so clear. On the other hand, BZN shows clearly the phase transition at lower temperature 1350°C [26]. **Figure 16(a)** shows *Qf* as a function of sintering temperature. Under the transition temperature such as 1200 and 1300°C, the sintered samples show order with under 50 × 103 GHz of *Qf*. Moreover, at 1400°C, higher than the transition

**15**

**Figure 14.**

*422(b).*

**Figure 15.**

**Figure 16.**

temperature, the *Qf* values increased to 90 × 103

This shows that the high symmetry form with disorder performs higher *Qf* than ordering form. Moreover, the sample annealed at 1200°C/100 h transformed to order form, but the *Qf* value did not improve and slightly decreased. Grain size and

*Qf (a), grain size (b) and density (c) as a function of sintering temperature of BZN ceramics.*

*The Qf as functions of ordering ratio (a), density (b) and grain size (c) of BZT ceramics.*

*XRPD patterns of BZT ceramics with different sintering times at 1350°C (a), here, asterisks are super lattice diffractions, and Magnified XRPD patterns around 2θ = 115° in which 420 diffraction peak split to 226 and* 

GHz with disordering structure.

*Dielectric Losses of Microwave Ceramics Based on Crystal Structure*

*DOI: http://dx.doi.org/10.5772/intechopen.82483*

*Dielectric Losses of Microwave Ceramics Based on Crystal Structure DOI: http://dx.doi.org/10.5772/intechopen.82483*

**Figure 14.**

*Electromagnetic Materials and Devices*

occupy *B*-sites statistically.

compositional density brings high *Qf*.

*2.3.2.1 Ordering ratio and Qf*

*2.3.2 Origin of high Q for microwave complex perovskite*

following three sets presented by Koga et al. [23, 25, 26, 63].

at about 80%, but the *Qf* values increase up to 100 × 103

*2.3.2.2 BZN with a clear order-disorder transition*

*2.3.1 Introduction*

in **Figure 13** [21]. In the ordered form of BMT, Mg2+ and Ta5+-ions located among the adjacent packing layers of BaO3 are ordering as -Mg-Ta-Ta-Mg-Ta-Ta-Mg-, as shown in **Figure 13**. On the other hand, in the disordered form, Mg2+ and Ta5+-ions

Kawashima et al. [14] presented that ordering brings a high *Q* based on BMT with long duration sintering, which showed high *Qf* and ordering. This has previously been believed to be the case because long duration sintering samples generally show high *Qf* and ordering. However, some examples have arisen that contradict this relation, such as BMT-Ba(Co1/3Ta2/3)O3 [59], BMT-BaZrO3 [60], BMT-BaSnO3 [61] and BZT-(SrBa)(Ga1/2Ta1/2)O3 [62]. Koga et al. [23–26] presented the relationship between high *Qf* and the ordering ratio as determined by the Rietveld method, the high *Qf* samples with disordered structure synthesised by spark plasma sintering (SPS) [63] and the effects of annealing of disordered BZN with an orderdisorder transition point of 1350°C [26]. HRTEM and Rietveld studies confirmed the ordering and disordering of BZN samples [64]. Partial ternary phase diagrams such as BaO-ZnO-Ta2O5, BaO-MgO-Ta2O5 and BaO-ZnO-Nb2O5 were studied on the composition with high *Qf* that deviated from the stoichiometric composition of BZT/BMT/BZN by Kugimiya et al. [22, 27], Koga et al. [24, 26] and Kolodiazhnyi [29]. Kugimiya pointed out that the solid solutions with high density and high *Qf* located on the tie-line BMT-Ba5Ta4O15, which have completed the ideal chemical formula without oxygen defects. It is one of the conditions for high *Q* that the high

In this section, it is explained that ordering has no relation with *Qf* based on the

The ordering of BZT was observed on the samples with high *Qf* sintered at 1350°C [23] over 80 h. **Figure 14** presents the XRPD patterns (**a**) with super lattice lines (asterisked), and the high angle diffraction patterns (**b**) which depicts splitting of 420 cubic diffraction peak into two peaks, namely 226 and 422 in the trigonal system. These data are consistent with the report by Kawashima et al. [14]. Koga et al. investigated the amount of BZT ceramic as ordering ratio by the Rietveld method [23], which is shown in **Figure 15(a)**. The ordering ratio saturates

effect of ordering on the *Qf* is not so significant. However, the *Qf* values are affected by density and grain size as shown in **Figure 15(b)** and **(c)**, respectively [15, 23].

Many complex perovskites such as BMT and BZT have the order-disorder phase transition at high temperature, and the order-disorder transition is not so clear. On the other hand, BZN shows clearly the phase transition at lower temperature 1350°C [26]. **Figure 16(a)** shows *Qf* as a function of sintering temperature. Under the transition temperature such as 1200 and 1300°C, the sintered samples show order

GHz of *Qf*. Moreover, at 1400°C, higher than the transition

GHz. This shows that the

**14**

with under 50 × 103

*XRPD patterns of BZT ceramics with different sintering times at 1350°C (a), here, asterisks are super lattice diffractions, and Magnified XRPD patterns around 2θ = 115° in which 420 diffraction peak split to 226 and 422(b).*

**Figure 15.** *The Qf as functions of ordering ratio (a), density (b) and grain size (c) of BZT ceramics.*

**Figure 16.** *Qf (a), grain size (b) and density (c) as a function of sintering temperature of BZN ceramics.*

temperature, the *Qf* values increased to 90 × 103 GHz with disordering structure. This shows that the high symmetry form with disorder performs higher *Qf* than ordering form. Moreover, the sample annealed at 1200°C/100 h transformed to order form, but the *Qf* value did not improve and slightly decreased. Grain size and densities as shown in **Figure 16(b)** and **(c)** also increased as the sintering temperature from 1200 to 1400°C [15, 26]. As if the sample sintered at 1400°C annealed at 1200°C/100 h, the grain size and densities were not changed. Because of annealing, the slight decrease in *Qf* might be a result of the low symmetry that accompanies order. On the contrary, Wu et al. [65] presented annealing of BZN at 1300°C brings high *Qf* with ordering. The annealing temperature is high enough for sintering, so sintering was proceeded with ordering the same as Kawashima's results [14].

The BZN samples A and B are also studied by XRPD and HRTEM, which sintered at 1400°C/100 h above the order-disorder phase transition point and subsequently annealed at 1200°C/100 h below the transition point, respectively [26, 64]. The two samples were identified by conventional XRPD as shown in **Figure 17(a)**. As the super lattice lines are not clear, the high angle XRPD patterns around 2*θ*~115° were measured (**Figure 17(b)**). On the XRPD pattern, the sample A shows a single peak of the 420 diffraction, so it was confirmed as disorder phase. On the other hand, the sample B shows the peak splitting of 422 and 226 depending ordering. These results are comparable with Koga's data [23]. These two samples were analysed by the Rietveld method.

HRTEM figures as shown in **Figure 18** for most area of sample A (**Figure 18(a)**) and B (**Figure 18(c)**) are disordered and ordered area along the [111]c direction, respectively. A fast Fourier transform (FFT) image is inserted in **Figure 18(a)** of a disordered area without further reflections along the [111]c direction and in **Figure 18(c)** of a ordered area with additional two reflection points for super lattice. In the both sample A and B, mixed area of disordered and ordered area existed in **Figure 18(b)**, and in the sample B, ordered area showing twin-related anti-phase domain boundary also existed as shown in **Figure 18(d)**. The FFT image of twin area shows superimposed of ordered diffractions with four additional points.

**Figure 19** depicts the high-resolution XRPD pattern of sample A and B using synchrotron radiation [64]. The super lattice diffraction 100 t peaks (reciprocal lattice plane 100 in the trigonal crystal system) are observed in both samples. The diffraction intensity of sample A is lower than that of sample B. These super lattice diffraction intensity peaks are comparable with the ordering ratios, that is the sample A and B have the value of 27.6 and 54.2%, respectively, obtained by the Rietveld method. Although the degree of ordering of sample B is large compared to that of sample A, it was assumed about 80% ordering for a whole sample, as in the case of BZT [23].

#### **Figure 17.**

*XRPD patterns for BZN ceramics sintered at 1400°C (sample A) and annealed at 1200°C (sample B) (a) and magnified high angle XRPD patterns around 2θ~115° (b).*

**17**

**Figure 19.**

*Here, subscript t is trigonal, and c is cubic.*

**Figure 18.**

*anti-phase domain boundary in sample B (d).*

*Dielectric Losses of Microwave Ceramics Based on Crystal Structure*

*HRTEM images of sample A and B with FFT image along the [111]c direction: disordered area in sample A (a), mixed area of disordered and ordered area in sample A (b), ordered area in sample B (c) and twin related* 

*High-resolution synchrotron XRPD patterns (λ = 0.82718 Å) for sample A and B with super lattice peak 100t.* 

*DOI: http://dx.doi.org/10.5772/intechopen.82483*

*Dielectric Losses of Microwave Ceramics Based on Crystal Structure DOI: http://dx.doi.org/10.5772/intechopen.82483*

#### **Figure 18.**

*Electromagnetic Materials and Devices*

tions with four additional points.

densities as shown in **Figure 16(b)** and **(c)** also increased as the sintering temperature from 1200 to 1400°C [15, 26]. As if the sample sintered at 1400°C annealed at 1200°C/100 h, the grain size and densities were not changed. Because of annealing, the slight decrease in *Qf* might be a result of the low symmetry that accompanies order. On the contrary, Wu et al. [65] presented annealing of BZN at 1300°C brings high *Qf* with ordering. The annealing temperature is high enough for sintering, so sintering was proceeded with ordering the same as Kawashima's results [14].

The BZN samples A and B are also studied by XRPD and HRTEM, which sintered at 1400°C/100 h above the order-disorder phase transition point and subsequently annealed at 1200°C/100 h below the transition point, respectively [26, 64]. The two samples were identified by conventional XRPD as shown in **Figure 17(a)**. As the super lattice lines are not clear, the high angle XRPD patterns around 2*θ*~115° were measured (**Figure 17(b)**). On the XRPD pattern, the sample A shows a single peak of the 420 diffraction, so it was confirmed as disorder phase. On the other hand, the sample B shows the peak splitting of 422 and 226 depending ordering. These results are comparable with Koga's data [23]. These two samples were analysed by the Rietveld method. HRTEM figures as shown in **Figure 18** for most area of sample A (**Figure 18(a)**) and B (**Figure 18(c)**) are disordered and ordered area along the [111]c direction, respectively. A fast Fourier transform (FFT) image is inserted in **Figure 18(a)** of a disordered area without further reflections along the [111]c direction and in **Figure 18(c)** of a ordered area with additional two reflection points for super lattice. In the both sample A and B, mixed area of disordered and ordered area existed in **Figure 18(b)**, and in the sample B, ordered area showing twin-related anti-phase domain boundary also existed as shown in **Figure 18(d)**. The FFT image of twin area shows superimposed of ordered diffrac-

**Figure 19** depicts the high-resolution XRPD pattern of sample A and B using synchrotron radiation [64]. The super lattice diffraction 100 t peaks (reciprocal lattice plane 100 in the trigonal crystal system) are observed in both samples. The diffraction intensity of sample A is lower than that of sample B. These super lattice diffraction intensity peaks are comparable with the ordering ratios, that is the sample A and B have the value of 27.6 and 54.2%, respectively, obtained by the Rietveld method. Although the degree of ordering of sample B is large compared to that of sample A, it was assumed about 80% ordering for a whole sample, as in the case of BZT [23].

*XRPD patterns for BZN ceramics sintered at 1400°C (sample A) and annealed at 1200°C (sample B) (a) and* 

**16**

**Figure 17.**

*magnified high angle XRPD patterns around 2θ~115° (b).*

*HRTEM images of sample A and B with FFT image along the [111]c direction: disordered area in sample A (a), mixed area of disordered and ordered area in sample A (b), ordered area in sample B (c) and twin related anti-phase domain boundary in sample B (d).*

#### **Figure 19.**

*High-resolution synchrotron XRPD patterns (λ = 0.82718 Å) for sample A and B with super lattice peak 100t. Here, subscript t is trigonal, and c is cubic.*

It is revealed that the degree of ordering increased from 27.6 to 54.2% due to the annealing. However, the *Qf* values, grain size and the density have no influence on the degree of ordering (**Figure 16**). While the disordered area of sample A (sintered above the transitional temperature) changes to the low-temperature phase with ordering by the annealing, the *Qf* values were expected to be increased. However, the *Qf* values changed only somewhat from 95.7 × 103 GHz to 95.0 × 103 GHz [64]. The effect of ordering is not acceptable to change the *Qf* value considerably.

## *2.3.2.3 BZT with disordering leaded high Qf by SPS*

The ordered and disordered BZT ceramics can be achieved by varying the sintering duration in the conventional solid-state reaction (SSR). A high density and high *Q* ceramics of ordered BZT were obtained by SSR with a long sintering time of over 80 h, while the disordered BZT was not possible to fabricate by using SSR. Koga et al. [63] reported the high density disordered BZT ceramics for a short sintering time of 5 mins by using spark plasma sintering (SPS). **Figure 20(a)** presents the *Qf* as a function of the densities of BZT fabricated using SSR and SPS [15, 63]. The fabricated SPS samples were shown to be disordered cubic type of perovskite as depicted in the XRPD pattern (**Figure 20(b)**) with a peak of 420 reflection in compared with the ordered trigonal type with peaks separations of 422 and 226 when sintered using SSR (1400°C 100 h). The ceramics were sintered at the temperature between 1150 and 1300°C under 30 Mpa pressure [63].

This may result in the disordered BZT with a high density of 7.62 g/cm3 , which is approximately 20% higher than that of low-density samples of 5.0–6.0 g/cm3 synthesized by conventional SSR. The full width at half maximum (FWHM) of the 420 peak became narrower with an increase in the temperature from 1100 to 1300°C (**Figure 20(b)**) indicates that the degree of crystallisation of the disordered cubic phase is improved without the need for conversion to the ordered trigonal phase. Regardless of the method of synthesis, *Qf* is strongly dependent on density, and *Qf* values were improved with increasing density. The dense disordered BZT ceramics synthesized by SPS showed a significantly high *Qf* (= 53.4 × 103 GHz) comparable to that of the ordered BZT with the same density (= ca. 7.5 g/cm3 ) synthesized by SSR. The crystallisation with densification of BZT ceramics should play a more critical role in the improvement of the *Q* factor in the BZT system rather than the structural ordering.

#### **Figure 20.**

*Qf of BZT by solid-state reaction (SSR) and spark plasma sintering (SPS) as a function of density, Disordered BZT by SPS shows high Qf (a). Nonsplitting XRPD patterns around 420 diffraction of BZT sintering by SPS with different sintering temperatures compared with ordered sample by SSR with splitting pattern (b).*

**19**

**Figure 21.**

*BaO-MgO-TaO5/2 partial system (BMT system).*

*Dielectric Losses of Microwave Ceramics Based on Crystal Structure*

*2.3.3 Deviated compositions with high Qf from stoichiometric complex perovskite* 

*2.3.3.1 The highest Qf composition with intrinsic compositional density by Kugimiya's* 

Kugimiya [22, 27] presented the highest *Qf* composition with intrinsic compositional density on the Ta and Ba rich side near the BMT-Ba5Ta4O15 tie-line in a BaO-MgO-TaO5/2 partial system (BMT system), as shown in **Figure 21**. He presented three areas divided by the following two lines as shown in **Table 1** and **Figure 21**.

= 5/4 (3)

= /2 (4)

Here, *α* and *γ* are as written in the formula *α*BaO·*γ*TaO5/2. On the *α* = 5*γ*/4 line, Ba1 + *α*(Mg1/3Ta2/3 + 4*<sup>α</sup>*/5*Vα*/5)O3+3*α* solid solutions are formed as the ideal compositions without vacancies in the *A*- and O-sites. In the *B*-site, the vacancy is neutralized and

In **Figure 21**, the composition with intrinsic compositional high density shows the highest *Q* of 50.0 × 103 on the tie-line between BMT and Ba5Ta4O15 ( = 5/4).

in the centre. The contour is elongated parallel to the *Q* max line as

drawn in **Figure 21,** and it changes steeply on the perpendicular to this line. So, the compositions without oxygen vacancy and with neutralised charge vacancies

in the outer area to

The contour lines in **Figure 21** show *Q* values from 2.0 × 103

In a BaO-Mg/ZnO-Ta2O5 partial ternary ceramic (BMT/BZT system), complex perovskite such as BMT and BZT are forming solid solutions, and the *Qf* values varied intrinsically based on the crystal structure in the solid solutions depending on the density and defects. In this section, the crystal structure and properties on the varied compositions from the stoichiometric complex perovskite composition

*DOI: http://dx.doi.org/10.5772/intechopen.82483*

are reviewed for high *Qf* research.

*composition*

*research*

without charge.

25.0 × 103

*Electromagnetic Materials and Devices*

the *Qf* values changed only somewhat from 95.7 × 103

between 1150 and 1300°C under 30 Mpa pressure [63].

synthesized by SPS showed a significantly high *Qf* (= 53.4 × 103

to that of the ordered BZT with the same density (= ca. 7.5 g/cm3

*2.3.2.3 BZT with disordering leaded high Qf by SPS*

It is revealed that the degree of ordering increased from 27.6 to 54.2% due to the annealing. However, the *Qf* values, grain size and the density have no influence on the degree of ordering (**Figure 16**). While the disordered area of sample A (sintered above the transitional temperature) changes to the low-temperature phase with ordering by the annealing, the *Qf* values were expected to be increased. However,

The ordered and disordered BZT ceramics can be achieved by varying the sintering duration in the conventional solid-state reaction (SSR). A high density and high *Q* ceramics of ordered BZT were obtained by SSR with a long sintering time of over 80 h, while the disordered BZT was not possible to fabricate by using SSR. Koga et al. [63] reported the high density disordered BZT ceramics for a short sintering time of 5 mins by using spark plasma sintering (SPS). **Figure 20(a)** presents the *Qf* as a function of the densities of BZT fabricated using SSR and SPS [15, 63]. The fabricated SPS samples were shown to be disordered cubic type of perovskite as depicted in the XRPD pattern (**Figure 20(b)**) with a peak of 420 reflection in compared with the ordered trigonal type with peaks separations of 422 and 226 when sintered using SSR (1400°C 100 h). The ceramics were sintered at the temperature

The effect of ordering is not acceptable to change the *Qf* value considerably.

This may result in the disordered BZT with a high density of 7.62 g/cm3

approximately 20% higher than that of low-density samples of 5.0–6.0 g/cm3 synthesized by conventional SSR. The full width at half maximum (FWHM) of the 420 peak became narrower with an increase in the temperature from 1100 to 1300°C (**Figure 20(b)**) indicates that the degree of crystallisation of the disordered cubic phase is improved without the need for conversion to the ordered trigonal phase. Regardless of the method of synthesis, *Qf* is strongly dependent on density, and *Qf* values were improved with increasing density. The dense disordered BZT ceramics

SSR. The crystallisation with densification of BZT ceramics should play a more critical role in the improvement of the *Q* factor in the BZT system rather than the

*Qf of BZT by solid-state reaction (SSR) and spark plasma sintering (SPS) as a function of density, Disordered BZT by SPS shows high Qf (a). Nonsplitting XRPD patterns around 420 diffraction of BZT sintering by SPS with different sintering temperatures compared with ordered sample by SSR with splitting pattern (b).*

GHz to 95.0 × 103

GHz [64].

, which is

GHz) comparable

) synthesized by

**18**

**Figure 20.**

structural ordering.
