Ferroelectric Materials

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Ferroelectric Systems

Raman Spectra of Soft Modes in Ferroelectric Crystals

Introduction

Characteristics of polar phonons

General properties of Polar phonons
General properties of soft modes

In general, the frequency of LO is higher than TO due to the depolarization field. The integrated intensity of the soft-mode Raman spectrum is related to the real part of the low-frequency dielectric constant ε(ω) via the Kramers–Krong relation and Eq. Different properties of the polar LO and TO phonon in a cubic crystal. a) LO/TO separation in space, (b) polariton dispersion, (c) dielectric constant, (d) IR reflectance spectrum, and (e) Raman spectrum.

Figure 1. Various properties of polar LO and TO phonon in a cubic crystal. (a) LO/TO splitting in space, (b) dispersion of polariton, (c) dielectric constant, (d) IR reflection spectra, and (e) Raman spectrum.

Intensity and line shape of Raman spectra
Generalized susceptibility and the stability limit

Fig.2 Movement of the pole of the susceptibility in the complex ω-plane as stability limit is approached. a) Damped harmonic oscillator, (b) General case, (c) Relaxation type (Debye). Movement of the pole of the susceptibility in the complex ω-plane as stability limit is approached. a) Damped harmonic oscillator, (b) general case, (c) relaxation type (Debye).

Figure 2. Motion of the pole of the susceptibility in the complex ω-plane as stability limit is approached

Raman spectrum of soft mode in KDP
Displacive or order–disorder ?
Influence of the ferroelectric domain

Different pole paths to the origin of the complex  -plane are shown for DHO. Later studies by different groups, however, revealed that the explanation of the origin of the phase transition by Kaminov et al.

Figure 4. Behavior of the generalized susceptibility GVWF in (ω 0 , γ, γ ′ ) space. Various paths of the pole to the ori‐

Ferroelectric SrTiO 3

Soft mode in STO16
Soft mode in SrTiO 3 18 (STO18)

This is another proof of the extremely strong polar nature of the ferroelectric soft mode in SrTiO3. The existence of the ferroelectric domains in the sample, especially the direction of the spontaneous polarization P→.

Figure 8. (a) Perovskite structure and the ferroelectric soft mode (Slater mode). (b) Blue and red squares are the unit cell in the cubic and the tetragonal phase, respectively

LO/TO splitting in the ferroelectric Ice-XI

Structure of Ice-XI
LO/TO splitting of the translational mode
Raman spectra of stretching modes in Ice-XI

The present result is the first experimental confirmation of the LO/TO split in ice. Another feature of the LO (A1/B2) mode at 237 cm−1 is the fact that the intensity is strong only in the spectra with polarization (cc).

Figure 15. (a) Raman spectra in a wide frequency range. Scattering geometry is a(c, ∗)b with no polarization analyzer.

Summary and conclusions

In Section 3, the physical meaning of the susceptibility χQ(ω), such as damped harmonic oscillator (DHO) and Debye-type relaxation, which are often used in the analysis of overdamped soft-mode Raman spectra, was discussed in terms of the proposed general susceptibility form (GVWF). Evidence of LO/TO splitting should be obtained by measuring the propagation direction dependence (K¯p) as shown in ice-XI.

Acknowledgements

In Section 6 , the first clear evidence of LO/TO splitting in proton-ordered (ferroelectric) translational mode Raman spectra in ice-XI was given. Overload mode analysis by computer assembly depends on the model and sensitivity function used.

Author details

In particular, the analysis of superimposed soft mode spectra using an arbitrary sensitivity can be very ambiguous. In Section 5, the special nature of the Raman spectra related to the ferroelectric transition of the ferroelectric isotope exchanged SrTiO3 (STO18) was discussed.

Origin of

Piezoelectricity in

Piezoelectric Ceramics from the Viewpoints of Elastic

How can high piezoelectricity be realized from measuring acoustic wave velocities?

In this endeavor, we report the acoustic wave velocities in piezoelectric ceramics measured with our developed method and the calculation results of Young's modulus, Poisson's ratio, modulus of rigidity and bulk modulus, especially to obtain high piezoelectricity in lead-free ceramics. Furthermore, we propose the design for R&D on piezoelectric materials from the point of view of measuring acoustic wave velocities.

Experimental procedure

Relationships between Young's modulus (Y) and coupling factors of transverse mode (k31) and longitudinal mode (k33) in piezoelectric ceramics and relaxor single crystals; giant k31 was realized in Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3. Relationships between the ratio of sound speeds (VS/VL), elastic constants and dielectric and piezoelectric constants.

4 Fig.2 Figure 2 Replace with the figure below because of lack of

Results and discussion

Relationship between sound velocity ratio (VS/VL) and planar coupling factor (kp) in lead-free and lead ceramics. In fact, it is the bulk density (ρ) of SZ that had the highest kp [5, 8] in the lead-free ceramics under investigation.

Figure 10). We believe that the origin of piezoelectricity in piezoelectric ceramics was due to large change in V S (-ΔV S ) while applying DC poling field parallel to the thickness of disks.

Lead-free

Kp increased linearly with decreasing VS/VL in lead-free ceramics as well as leaded ceramics such as PZT, PLT and PT. It was said that the direction of R&D on lead-free piezoelectric ceramics with high piezoelectricity was looking for ceramics with lower bulk density.

Lead-containing SZ

When we research and develop new piezoelectric ceramics with high piezoelectricity in lead-free ceramics, we need a new concept that is different from the conventional research that is looking for chemical compositions such as MPB [25]. From the above results, we came to an important concept to obtain lead-free ceramics with high piezoelectricity, namely the R&D on lead-free ceramics with a lower mass density.

Lead-containing

Conclusions in this part

In addition, the origin of piezoelectricity in piezoelectric ceramics could be explained by the elastic constants before and after DC poling. Effects of firing and DC poling treatments on elastic constants measured by acoustic wave velocities in barium titanate piezoelectric ceramics.

Effects of firing and DC poling treatments on elastic constants measured from acoustic wave velocities in barium titanate piezoelectric ceramics

Introduction
Experimental procedure
Results and discussion
Conclusions in this part

Changes in (a) Young's modulus (ΔY) and (b) Poisson's ratio (Δσ) in BT02 and BT05 ceramics during DC poling. BT02 before poling BT02 after poling BT05 before poling BT05 after poling. a) stiffness modulus (G) and (b) bulk modulus (K) in BT02 and BT05 ceramics before and after DC poling.

Figure 13. Firing temperature (F T ) vs. (a) relative dielectric constant (ε r ), (b) planar coupling factor (k p ) for radial mode on disks, (c) frequency constant (fc p ), and (d) piezoelectric strain d 33 constant in BT02 and BT05 ceramics before and a

Summary of this chapter

Effect of domain switching and rotation on dielectric and piezoelectric properties in lead zirconate titanate ceramics. Polishing field dependence of ferroelectric properties in barium titanate ce‐. Alkaline niobate-based lead-free piezoelectric ceramics.

Perovskite-Based Mesostructures and Related Composites — Influence Exerted

Experimental processing

NaNbO 3 synthesis
Reaction Mechanism to form Na 2 Nb 2 O 6 .H 2 O and NaNbO 3
NaNbO 3 particles characterization

The dehydration of Na2Nb2O6.nH2O promotes the formation of NaN-bO3 perovskite phase, which is energetically more stable [20]. The PL emission region observed here is not the same for Na2Nb2O6.nH2O, which presents fiber-like particles to start [22].

Figure 1. XRD patterns of particles obtained by microwave hydrothermal synthesis using 300 W at 180°C in different synthesis time.

Composite processing

Polymer matrix: PVDF
Obtaining NaNbO 3 1D nanostructures modified by polyaniline (PAni)
Fabrication of composite
Composite characterization

Near the penetration threshold, the value of the electrical conductivity and dielectric constant of the composition increases suddenly by several orders of magnitude. To calculate the penetration threshold of the composites, electrical conductivity and dielectric constant measurements were performed at 1 kHz for different rates (matrix/dispersed phase).

Figure 6. FE–SEM image of (A) NaNbO 3 fiber-like particles covered with reprotonated PAni and (B) larger image.

Conclusion

An increase in the amount of ceramic particles causes a loss of flexibility in the composite due to a change in the bonding between the ceramic particles and the polymer. The characterization of composite materials shows the importance of conductivity due to the fact that these materials have a multimodal microstructure and that each phase has intrinsic properties that determine the properties and applications of the designed composite.

Polarization and

Thermally Stimulated Processes in Lead-Free Ferroelectric Ceramics

Ferroelectric behaviour and pyroelectricity in ferroelectric materials
Experimental Procedure

Sample preparation
Ferroelectric measurements and thermally stimulated discharge current experiments Polarization-electric field (P–E) loops were obtained at room temperature for 10 Hz by using

Ferroelectric properties
Thermally stimulated processes and pyroelectricity
Ferroelectric and pyroelectric parameters

Conclusions

Values of the remanent polarization (Pr), Pr/Pmax relationship and the constraint field (Ec) for the studied samples at room temperature. Values of the remanent polarization (Pr), the pyroelectric coefficient (p), and the current response parameter (RV).

Figure 1 shows the structure for some Aurivillius systems with m=1, m=2 and m=3, at the paraelectric phase, as examples

Role of Ca off-Centering in Tuning Ferroelectric Phase

Transitions in Ba(Zr,Ti)O 3 System

Effects of Ca substitution in BaTiO 3

Crystal growth
Dielectric behaviors

Similar to the polycrystalline ceramics[12], the Curie point was almost independent of the Ca concentration. The temperature dependence of the soft-mode frequency agreed qualitatively with the dielectric permittivity through Lyddane–.

≤ 0.34 with a high growth rate of 20 mm/h.[6] Fig. 3(b) shows a rod of crystal obtained by this method

Ca x TiO 3 Sing crystal

Phase diagram and quantum phase transitions

Comparison of (a) dielectric permittivity of (Ba1-xCax)TiO3 single crystals and (b) the phonon frequency of the Slater soft-mode. Interestingly, a dielectric anomaly was observed for the T-O quantum phase transition at x= xcT-O as shown to the right of the bottom panel in Fig.

Figure 6. Comparison of (a) dielectric permittivity of (Ba 1-x Ca x )TiO 3 single crystals and (b) the phonon frequency of the Slater soft-mode.

Ca x TiO 3 x=0

Ca off-centering predicted from first principles calculations
Polarization and strain responses
Effects of Ca-substitution in the Ba(Ti,Zr)O 3 solid solution

Phase formation and structure transformation at room temperature
Phase evolution with temperature
Polarization and strain responses under an electric field

Summary

The substitution of Ca for Ba will absolutely lead to the shrinkage of the perovskite unit cell. 11(d), a Ca off-centering shift leads to the lowering of the potential energy of the system.

Figure 8. Change of the inverse dielectric susceptibility (χ=ε-1) near the T-O phase transition in (Ba 1-x Ca x )TiO 3 crystals.

Dynamic Amplification of Optical Signals by Photorefractive Ferroelectric Liquid Crystals

Ferroelectric liquid crystals

Structures of the SmC phase and the SS state of the SmC phase (SS-FLC). Structures of the SmC phase and the SS state of the SmC phase (SS-FLC).

Figure 3. Structures of the nematic and smectic phases.

Asymmetric energy exchange in photorefractive materials

Two laser beams interfere in the SS mode of the mixture of FLC/photoconductive compound; (b) charge generation occurs at the bright regions of the interference fringes;. A schematic illustration of the setup used for the two-beam coupling experiment is shown in Figure 9(a) .

Figure 8. Schematic illustrations of (a) photochromic and (b) photorefractive gratings.

Photorefractive effect of FLCs

Two-beam coupling experiments on FLCs
Effect of the applied electric field magnitude
Refractive index grating formation time

As the strength of the external electric field increased, the enhancement coefficient of SCE8 doped with 0.5 wt% to 1 wt% CDH increased. Temperature dependence of (a) the enhancement coefficient and (b) spontaneous polarization for a FLC (SCE8) mixed with 2 wt% CDH and 0.1 wt% TNF.

Figure 10. Structures of the photoconductive compound CDH and the sensitizer TNF.

Photorefractive effect in photorefractive FLC blends containing photoconductive chiral compounds

Photoconductive chiral dopants
Asymmetric energy exchange in photorefractive FLC blends
Temperature dependence of the asymmetric energy exchange for photorefractive FLC blends
Effect of the photoconductive chiral dopant concentration
Dynamic amplification of optical images in photorefractive FLC blends
Dynamic holograms formed in FLC blends

On the other hand, the spontaneous polarization of the 3T-2OC samples was about 5 nC/cm2. Refractive index lattice formation times (reaction time) for (a) mixtures of the base LC, 3T-2MB (2-10 wt.

Figure 17. Structures of the smectic LCs (8PP8, 8PP10, and 8PP6), photoconductive chiral dopants (3T-2MB and 3T-2OC), and the sensitizer TNF.

Conclusions

This result shows that a hologram image is formed at the interference area in the FLC material and this contributes to the optical image amplification. The SLM modulated the object beam (488 nm), which was irradiated onto the FLC sample and al-.

New Properties and Applications of Polyvinylidene- Based Ferroelectric Polymer

Method

Details on the preparation of PVDF-based polymer films using the LB technique are described below. Horizontal transfer of LB technique: (a) and (b) processing of LB films; (c) transfer of the PVDF-based film to the substrate.

Dielectric tunability properties of PVDF-based polymer

The P(VDF-TrFE-CFE) shows a typical relaxor of temperature dependences of the dielectric constant and dielectric loss versus frequency, as shown in Fig. In our opinion, they should be associated with the special microstructure of the terpolymer LB films.

Huge electrocaloric effect in LB ferroelectric polymer thin films

Thus, the greater the ECE of the work material, the better the cooling efficiency. As the applied field is reduced, the temperature of the material drops back to the temperature of the cooling charge.

Ferroelectric-like phase transition in P(VDF-TrFE-CFE) terpolymer ultrathin films

The temperature dependence of the complex permittivity of the terpolymer films measured at 1 kHz in the heating process is shown in Fig. In addition, the temperature dependence of the C-V curves of the terpolymer film with one monolayer has been measured and shown in Fig.

Figure 5. Polarizations from P-E loops and adiabatic temperature change T versus temperature in different electric fields for (a) P(VDF-TrFE) films and(b) P(VDF-TrFE-CFE) films

Abnormal polarization switching of relaxor terpolymer films at low temperature

The temperature dependence of the ferroelectricity of terpolymer P (VDF-TrFE-CFE) films were systematically investigated. These differences are considered to be caused by the existence of the less polar TTTG conformation in the ferroelec‐.

Figure 7. The temperature dependence of C-V curve at 10 kHz for one transferred layer terpolymer film

The creep process of the domain switching in P(VDF-TrFE) ferroelectric thin films

The creep process of the domain switching in P(VDF-TrFE) ferroelectric thin films thin films. The domain wall, which is assumed to have a shape like a thin plate, propagates slowly, corresponding to n=1, until the completion of the domain switching in the lamellae.

Self-polarization in ultrathin LB polymer films

This may be due to back switching of domains after removal of the positive pole voltage. This was considered to be a result of the self-polarization of the ultrathin P(VDF-TrFE) polymer film due to the preferred alignment of the dipoles on the Al substrates.

Electronic transport property in ferroelectric polymer films

It also suggests that the preferred polarization of the fresh device is aligned from the bottom electrode to the surface of the P(VDF-TrFE) film. The temperature dependence of the I-V behavior from 100 K to 350 K was measured and the temperature dependence of the current density under voltage 5 V (about 70 MV/m) is shown in Fig.

Figure 12. Pyroelectric voltage of the device under infrared radiation (a) before poling, (b) after poling at -1 V, (c) after poling at +1 V, and (d) 12 h after poling at -1 V

Enhanced electric properties in the artificial polymer multilayers

The temperature dependence of the Pr of the multilayers with different periodic thicknesses is summarized in the inset of Fig.

Figure 14 shows the XRD patterns of the multilayers with different periodicities. Two diffrac‐

Polarization switching properties of PVDF homopolymer films

In this study, the film thickness dependence of the Ecof the PVDF homopolymer LB films is investigated. In this study, the film thickness dependence of the Ec of the PVDF homopolymer LB films is investigated.

Conclusion

The ferroelectric P-E loops of the PVDF homopolymer and P(VDF-TrFE) films are shown in Fig. In addition, many special characteristics of these films have been generalized. a) The P-E loops of the PVDF homopolymer LB films with 10 to 200 transferred layers.

Multiferroics

O 3 Nanoparticles Embedded in SiO 2 Glass Matrix — A Colossal Dielectric and Magnetodielectric Response

Experimental details
Structural studies through transmission electron microscopy (TEM) and X-ray diffraction (XRD): Typical data are shown for Er 2 O 3 :SiO 2 NPs-glass composite system having 0.5 mol%
Dielectric and magnetodielectric (MD) effect

The MD response is highly dependent on the superparamagnetic property of the rare earth ions. Compositions of the Si(OC2H5)4 (TEOS), H2O and C2H5OH solutions used in the sol-gel process.

Table 1. Compositions of the Si(OC 2 H 5 ) 4 (TEOS), H 2 O, and C 2 H 5 OH solutions used in the sol–gel process.

O 3 NPs-glass composite system: colossal enhancement of dielectric constant and large MD effect

Temperature dependence dielectric response
Dielectric relaxation analysis
Polarization studies
Equivalent circuit analysis
Magnetodielectric effect
Micro-structural correlated resistivity analysis

The high dielectric value associated with DPT behavior (Figure 3(b)) decreases with increasing calcined temperature (i.e., Er2O3 NPs size). Color online) (a) Dielectric loss tanδ of Er05-8 at different frequencies, (b) Representative Arrhenius plot of the relaxation time of Er05-8.