A Transition From Relaxor To Normal Ferroelectric: An Overview

2006

A first-principles-based model is developed to investigate the influence of lead vacancies on the properties of relaxor ferroelectric Pb(Sc1/2Nb1/2)O3 (PSN). Lead vacancies generate large, inhomogeneous, electric fields that reduce barriers between energy minima for different polarization directions. This naturally explains why relaxors with significant lead vacancy concentrations have broadened dielectric peaks at lower temperatures, and why lead vacancies smear properties in the neighborhood of the ferroelectric transition in PSN. We also reconsider the conventional wisdom that lead vacancies reduce the magnitude of dielectric response.

Ferroelectrics Letters Section, 2001

Polarization-electric field (P-E) hysteresis loops and domain structures have been measured as a function of temperature in relaxor-based ferroelectric single crystal (PbZn,/3Nb2/303)0.9~j(PbTi03)o.o~s (PZN-8.5%PT). In order of increasing temperature, PZN-8.5%PT undergoes successive phase transitions: rhombohedra1 phase (below-375 K) + coexistence of rhombohedral and tetragonal phases (between-375 and-390 K)-f tetragonal phase (between-390 and-420 K)-+ coexistence of tetragonal and cubic phases (between-420 and-460 K)-+ cubic phase (above-460 K). Phase coexistence suggests an inhomogeneous distribution of Ti4+ concentration in the PZN-8.5%PT crystal.

physica status solidi (b), 2005

The relaxor ferroelectrics showing diffuse phase transition (DPT) are promising materials for multilayer ceramic capacitors because of their high dielectric permittivity in the vicinity of the so called DPT. This physical parameter is also important in the fine piezoelectric, pyroelectric and electro optic performance of relaxor ferroelectrics. The dielectric behavior of these materials shows that the ferroelectricparaelectric transition is diffuse. Also, there is a frequency dispersion of the real and imaginary parts of the dielectric permittivity and a deviation from the Curie -Weiss law. Many models have been developed to explain this phenomenon, but the exact mechanism associated to this dielectric behavior has not been established yet. This paper presents an analysis of the dielectric behavior in PLZT ferroelectric ceramics by using a new multi-Debye relaxation model, which does not make assumptions that involve the microstructure or possible correlation mechanisms.

Journal of the American Ceramic Society, 2005

The relaxor ferroelectric lead zinc niobate (Pb(Zn 1/3 Nb 2/3 )O 3 ) methods, such as optical microscopy on acid-etched samples 7 has been intensively investigated, because of its large dielecor transmission electron microscopy (TEM) on mechanically tric and piezoelectric properties for applications in actuathinned samples. 4 However, the dynamic observation of switchtors and transducers. In this study, the in-situ behavior of ing domains under an applied electric field or with changing the domains in Pb(Zn 1/3 Nb 2/3 )O 3 single crystals has been temperature has been difficult experimentally, which has observed using optical microscopy in combination with a resulted in limited research efforts. 8-11 charge-coupled device (CCD) camera. The temperature of An optical technique has been used to explore the growth of the sample has been cycled between ؊185؇C and ؉200؇C, macrodomains (Ͼ0.1 m) from microdomains (ϳ20 nm and while applying an electric field of up to ؎10 kV/cm. Many 0.1 m) in PZN single crystals along the ͗111͘ direction, as characteristics, such as the induction of birefringence, the functions of temperature and applied electric field. The meatransition between the microdomains and macrodomains, sured dielectric constant d* 33 and tan ␦, as a function of temperaand the "freeze-in" of the macrodomains, have been optiture for a poled sample, are compared to the optically observed cally observed. The optical and dielectric data have been macrodomain motion in an attempt to develop a fundamental collected and plotted as a function of temperature and understanding of the relaxor behavior in PZN. The focus of this electric field. An electric-field-temperature diagram showpaper is to develop an electric-field-temperature diagram that ing five domain-related regions has been proposed. The describes the domain behavior in PZN. Optically and electrimicrodomain-to-macrodomain phase transitionlike behavcally measured characteristics will be used to develop the difior seems to be an analog of a martensitic phase transition. ferent phase fields.

Ceramic Materials [Working Title]

This chapter presents the investigation of fabrication and the physical properties of the Pb(Zr1−xTix)O3-Pb(Zn1/3Nb2/3)O3-Pb(Mn1/3Nb2/3)O3 multicomponent ceramics. The multicomponent yPb(Zr1−xTix)O3-(0.925 − y)Pb(Zn1/3Nb2/3)O3-0.075Pb(Mn1/3Nb2/3)O3 (PZT-PZN-PMnN) ceramics were synthesized by conventional solid-state reaction method (MO) combined with the B-site oxide mixing technique (BO). Research results show that the electrical properties of PZT-PZN-PMnN ceramics are optimal at a PZT content of 0.8 mol and Zr/Ti ratio of 48/52. At these contents, the ceramics have the following optimal properties: electromechanical coupling factor, kp = 0.62 and kt = 0.51; piezoelectric constant (d31) of 130 pC/N; mechanical quality factor (Qm) of 1112; dielectric loss (tan δ) of 0.005; high remanent polarization (Pr) of 30.4 μC.cm−2; and low coercive field (EC) of 6.2 kV.cm−1. Investigation of the domain structure of the two ferroelectric phases (tetragonal and rhombohedral) in the ZnO-doped PZT...

Advances in Ferroelectrics, 2012

Physical Review Letters, 2009

Despite intensive studies on PbðMg 1=3 Nb 2=3 ÞO 3 (PMN) relaxor, understanding the exact nature of its giant dielectric response and of its physical ground state is a fundamental issue that has remained unresolved for decades. Here, we report a comprehensive study of PMN relaxor crystal, and show that (i) its anomalous dielectric behavior in a broad temperature range results from the reorientation of polarization in the crystal, and (ii) the PMN relaxor is essentially a nanosized ferroelectric material with multiscale inhomogeneities of domain structure in addition to the well-known inhomogeneities of chemical composition and local symmetry. Such inhomogeneities are believed to play a crucial role in producing the huge and enigmatic physical effects in relaxor system, and may be used to design other new systems with giant effects such as a relaxor system.

Journal of the European Ceramic Society, 2006

Data of the extensive study of dielectric response of relaxor PbMg 1/3 Nb 2/3 O 3 (PMN) single crystals, ceramics (standard and textured) and thin films (thickness 500 nm, sapphire substrate) in the broad frequency range (3 × 10 −3 to 10 14 Hz) were combined, summarized and analyzed. Influence of the mesoscopic structure, possible strain and defects in ceramics and thin film on both relaxational and phonon dynamics is discussed. The phonon response of PMN single crystal and thin film appears to be very similar, including the soft mode behaviour. Similar to PMN crystals, the dielectric response of PMN ceramics and films is mainly determined by relaxational dynamics of polar nanoclusters. Flipping and breathing of the clusters are assumed to be the dominant mechanisms, which can be resolved in the frequency spectra of the complex permittivity. The mesoscopic structure and defects in the ceramics do not result in any significant contribution to additional mechanisms, but influence the dynamics of nanoclusters and lead to pinning of the flipping contribution. In thin films the dielectric response due to cluster dynamics is much more reduced.

Journal of Materials Science, 2014

The influence of the barium concentration on the dielectric response of Sr 1-x Ba x Bi 2 Nb 2 O 9 system, with x = 0, 15, 30, 50, 70, 85, 100 at.%, has been studied. The barium concentration dependence of T m , as well as the temperature of the corresponding maximum for the real part of the dielectric permittivity, has suggested a cation site mixing among atomic positions, which has been supported by the structural analysis. A transition from normal ferroelectric-paraelectric phase transition to a relaxor behavior has been observed in the studied samples, when the barium concentration has increased. The relaxor behavior has been discussed.

Applied Physics Letters, 2009

Tetragonal tungsten bronze-structured materials based on lead metaniobate ͑PbNb 2 O 6 ͒ were studied in terms of thermal dynamics of dielectric properties, showing ferroelectric-to-paraelectric phase transition of diffuse and relaxor type in some specific cases. These features are normally ascribed to defects-induced structural disorder and compositional fluctuations associated with an arbitrary lattice site occupation between dopant and host ions. Nevertheless, for these lead metaniobate-based materials, the drastic change in the phase transition from normal to diffuse and relaxor is shown to take place when dopants are able to significantly shift the transition toward low temperatures, where these compounds are known to exhibit incommensurate superstructures that naturally present diffuse and relaxor dielectric characteristics.