1. Introduction

As we know, ferroelectric ceramics were first found in barium titanate ceramic with the ferroelectricity in the 1940s [1]. Since that time, the ferroelectric material with high resistivity, good fatigue resistance characteristic and high dielectric constant, pyroelectric detector, uncooled infrared detectors, uncooled infrared focal plane arrays and ferroelectric memory, and other

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

fields has great application prospect [2–5]. In recent years, complex mixed-ion ferroelectric materials have been extensively investigated in order to achieve optimum properties as well as to understand the underlying factors for property tweaking [6–9]. Therefore, the ferroelectric materials are considered to be one of the most practical materials in the future.

2. Experiment details

be found elsewhere [13].

2.2. Raman experiment details

800 K with a resolution of 0.1 K.

3. Results and discussion

3.1. PbTiO3-based single crystals

2.1. Fabrication of ferroelectric materials

The ferroelectric single crystals have been grown by a high temperature solution method (flux method) [13, 14]. High-purity powders were selected as starting materials. The raw material powders were stoichiometrically weighed, mixed by milling with zirconia media in the ethanol as a solvent. After drying. The powders were calcined at a certain temperature for hours to form the desired perovskite phase. Details of the fabrication process for the single crystals can

Structural Transformations in Ferroelectrics Discovered by Raman Spectroscopy

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The bulk ceramics were fabricated by a conventional solid state reaction sintering, using the appropriate amount of reagent grade raw materials [15, 16]. The samples were sintered at different temperature for several hours in air atmosphere, and then remilled for several hours to reduce the particle size for sintering. The calcined powders were added with 8 wt.% polyvinyl alcohol (PVA) as a binder. Before Raman measurements, the ceramics with the diameter of 15 mm and the thickness of 1 mm were rigorously single-side polished and cleaned in pure

Raman scattering experiments were carried out using a Jobin-Yvon LabRAM HR 800 UV micro-Raman spectrometer, excited by 632.8 nm He-Ne laser or 488 nm Ar laser and recorded

temperature Raman spectra, we choose a 50 microscope with a long working distance of 18 mm. The spectrometer grating can be choosed by 600, 1800 or 2400 grooves/mm grating which is depending on the different excitation wavelength. In order to learn more about the variation trend of vibration modes, all of the experimental spectra were fitted with independent damped harmonic oscillators. The polarized Raman spectra were recorded in backscattering geometry in parallel <x|zx|y > (VH) and perpendicular <x|zz|y > (VV) polarization configurations. Temperature dependent Raman spectra were collected with a THMSE 600 heating/cooling stage (Linkam Scientific Instruments) in the temperature range from 77 to

PbTiO3 (PT)-based perovskite compounds are important multifunctional materials, which have been investigated in the last half century due to their controllable physical properties. Most recently, the research hotspot for PbTiO3-BiMeO3 ferroelectrics have stimulated much interest [14]. A range of compelling information on thermal expansion behavior and lattice dynamics of novel ferroelectric perovskite-type 0.62PbTiO3-0.38Bi(Mg0.5Ti0.5)O3 (PT-BMT) single crystal has been revealed by means of temperature-dependent X-ray diffraction and polarized Raman scattering. Figure 1 shows the polarized Raman spectra of 0.62PT-0.38BMT single

. For the different

ethanol with an ultrasonic bath and rinsed several times by deionized water.

in the frequency range of 10–1000 cm<sup>1</sup> with a spectral resolution of 0.5 cm<sup>1</sup>

The ABO3 ferroelectric materials have achieved wide usage owing to their superior electromechanical properties (Scheme 1 shows the typical structure). Investigations of bulk ferroelectric materials have demonstrated good macroscopic homogeneity of their properties and clear ferroelectric behavior [2]. However, the development of knowledge about ferroelectric behavior at the submicrometer level is relatively slow. It has been found that the structural and chemical factors such as grain size, strain, stoichiometric and compositional homogeneity and phase structure, have great effect on optimization and reproducibility of the property coefficients in ferroelectric materials [10–12]. Therefore, a further investigation should be necessary in order to illustrate the physical mechanism in these ferroelectrics.

It is important to remember that the experimentally obtained parameters depend primarily on the spatial magnitude and time-scale of the measured physical phenomena, especially for studying the structure–property correlations in these materials. Raman spectroscopy is a sensitive technique for investigating the structure modifications and lattice vibration modes, which can give the information on the changes of lattice vibrations and the occupying positions of doping ions. Structural changes that alter the crystal symmetry often have a significant effect on the Raman spectrum. In addition, spatially resolved Raman spectroscopy can be used to probe the chemical homogeneity at sub-micrometer levels. This chapter provides a review of systematic Raman scattering study on the phase transition behavior in perovskites, tungsten bronze, Aurivillius layered, multiferroics and lead-free bulk materials. The effect of A- and B-site substitutions on the Raman spectra and phase transition behavior of these materials have been studied in detail. This chapter is arranged in the following way. In Section 1, research background; In Section 2, detailed growths of the ferroelectric materials and Raman experiment; In Section 3, results of Raman spectra in PbTiO3-Bi(Mg0.5Ti0.5)O3 (PT-BMT), SrxBa1xNb2O6 (SBN), Pb11.5xLaxZr0.42Sn0.4Ti0.18O3 (PLZST), Bi1xLaxFe1yTiyO3 (BLFT) and (K0.5Na0.5)NbO3-0.05LiN bO3 (KNN-LN); at last, the main results and remarks are summarized.

Scheme 1. Schematic representation of the typical ABO3 ferroelectric structure.
