A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Perspective on the Development of Lead-free Piezoceramics

Multiferroics, defined for those multifunctional materials in which two or more kinds of fundamental ferroicities coexist, have become one of the hottest topics of condensed matter physics and materials science in recent years. The coexistence of several order parameters in multiferroics brings out novel physical phenomena and offers possibilities for new device functions. The revival of research activities on multiferroics is evidenced by some novel discoveries and concepts, both experimentally and theoretically. In this review, we outline some of the progressive milestones in this stimulating field, especially for those single-phase multiferroics where magnetism and ferroelectricity coexist. First, we highlight the physical concepts of multiferroicity and the current challenges to integrate the magnetism and ferroelectricity into a single-phase system. Subsequently, we summarize various strategies used to combine the two types of order. Special attention is paid to three novel mechanisms for multiferroicity generation: (1) the ferroelectricity induced by the spin orders such as spiral and E-phase antiferromagnetic spin orders, which break the spatial inversion symmetry; (2) the ferroelectricity originating from the charge-ordered states; and (3) the ferrotoroidic system. Then, we address the elementary excitations such as electromagnons, and the application potentials of multiferroics. Finally, open questions and future research opportunities are proposed.

Multiferroicity: the coupling between magnetic and polarization orders

Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries.

Nanocomposites, a high performance material exhibit unusual property combinations and unique design possibilities. With an estimated annual growth rate of about 25% and fastest demand to be in engineering plastics and elastomers, their potential is so striking that they are useful in several areas ranging from packaging to biomedical applications. In this unified overview the three types of matrix nanocomposites are presented underlining the need for these materials, their processing methods and some recent results on structure, properties and potential applications, perspectives including need for such materials in future space mission and other interesting applications together with market and safety aspects. Possible uses of natural materials such as clay based minerals, chrysotile and lignocellulosic fibers are highlighted. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors of the aerospace, automotive, electronics and biotechnology industries.

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Nanocomposites: synthesis, structure, properties and new application opportunities

Due to the nature of domains, ferroics, including ferromagnetic, ferroelectric, and ferroelastic materials, exhibit hysteresis phenomena with respect to external driving fields (magnetic field, electric field, or stress). In principle, every ferroic material has its own hysteresis loop, like a fingerprint, which contains information related to its properties and structures. For ferroelectrics, many characteristic parameters, such as coercive field, spontaneous, and remnant polarizations can be directly extracted from the hysteresis loops. Furthermore, many impact factors, including the effect of materials (grain size and grain boundary, phase and phase boundary, doping, anisotropy, thickness), aging (with and without poling), and measurement conditions (applied field amplitude, fatigue, frequency, temperature, stress), can affect the hysteretic behaviors of the ferroelectrics. In this feature article, we will first give the background of the ferroic materials and multiferroics, with an emphasis on ferroelectrics. Then it is followed by an introduction of the characterizing techniques for the loops, including the polarization–electric field loops and strain–electric field curves. A caution is made to avoid misinterpretation of the loops due to the existence of conductivity. Based on their morphologic features, the hysteresis loops are categorized to four groups and the corresponding material usages are introduced. The impact factors on the hysteresis loops are discussed based on recent developments in ferroelectric and related materials. It is suggested that decoding the fingerprint of loops in ferroelectrics is feasible and the comprehension of the material properties and structures through the hysteresis loops is established.

Decoding the Fingerprint of Ferroelectric Loops: Comprehension of the Material Properties and Structures

The dielectric and ferroelectric properties of ( x )Pb(Mg 1/3 Nb 2/3 )O 3 –(1 − x ) Pb(Zr 0.52 Ti 0.48 )O 3 (where x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) ceramics prepared by an oxide-mixing method are measured by means of an automated dielectric measurement set-up and a modified Sawyer-Tower circuit, respectively. The dielectric properties of the ceramics are measured as functions of both temperature and frequency. The results indicate that the dielectric properties of the pure-phase PZT and PMN are of normal and relaxor ferroelectric behaviors, respectively. The dielectric behaviors of the 0.1PMN–0.9PZT and 0.3PMN–0.7PZT ceramics are more of normal ferroelectrics, while the other compositions are obviously of relaxor ferroelectrics. In addition, the transition temperature decreases and the maximum dielectric constant increases with increasing PMN content in the system. The P – E hysteresis loop measurements demonstrate that the ferroelectric properties of the ceramics in PMN–PZT system change gradually from the normal ferroelectric behavior in PZT ceramic to the relaxor ferroelectric behavior in PMN ceramic. These results clearly show the significance of PMN in controlling the electrical responses of the PMN–PZT system.

Dielectric and ferroelectric properties of lead magnesium niobate–lead zirconate titanate ceramics prepared by mixed-oxide method

The scaling behavior of the dynamic hysteresis of ferroelectric bulk system was investigated. The scaling relation of hysteresis area ⟨A⟩ against frequency f and field amplitude E0 for the saturated loops of the soft lead zirconate titanate bulk ceramic takes the form of ⟨A⟩∝f−1∕4E0, which differs significantly from that of the theoretical prediction and that of the thin film. This indicates that the scaling relation is dimension dependent and that depolarizing effects in the interior must be taken into account to model bulk materials. Additionally, the scaling relation for the minor loops takes the form of ⟨A⟩∝f−1∕3E03, which is identical to that of the thin film as both cases contain similar 180° domain-reversal mechanism.

Scaling behavior of dynamic hysteresis in soft lead zirconate titanate bulk ceramics

In this paper, the potential use of either amine-functionalized or hydroxyl-functionalized magnesium ferrite (MgFe2O4) nanoparticles (NPs) as Congo red nanoadsorbents is explored and compared. The ...

Amine-Functionalized and Hydroxyl-Functionalized MagnesiumFerrite Nanoparticles for Congo Red Adsorption

The temperature scaling of the dynamic hysteresis was investigated in soft ferroelectric bulk ceramic. The power-law temperature scaling relations were obtained for hystersis area ⟨A⟩ and remnant polarization Pr, while the coercivity EC was found to scale linearly with temperature T. The three temperature scaling relations were also field dependent. At fixed field amplitude E0, the scaling relations take the forms of ⟨A⟩∝T−1.1024, Pr∝T−1.2322, and (EC0−EC)∝T. Furthermore, the product of Pr and EC also provides the same scaling law on the T dependence in comparison with ⟨A⟩.

Temperature scaling of dynamic hysteresis in soft lead zirconate titanate bulk ceramic

The scaling behavior of the dynamic hysteresis of ferroelectric BaTiO3 single crystals was investigated. Two sets of the scaling relation of hysteresis area ⟨A⟩ against frequency f and field amplitude E0 were clearly established. Above the coercive field, the scaling took a form of ⟨A⟩∝f−0.195E00.950. On the other hand, the scaling in the form of ⟨A⟩∝f1.667E0−2.804E04.157 was obtained under subcoercive field condition. While these scaling relations were generally comparable to previously reported ones, it was found that the f and E0 exponents depended on E0 and f, respectively, which was in contrast to the prior theoretical prediction and experimental investigations.

Supon Ananta

Papers

Dielectric and ferroelectric properties of lead magnesium niobate–lead zirconate titanate ceramics prepared by mixed-oxide method

Scaling behavior of dynamic hysteresis in soft lead zirconate titanate bulk ceramics

Amine-Functionalized and Hydroxyl-Functionalized MagnesiumFerrite Nanoparticles for Congo Red Adsorption

Temperature scaling of dynamic hysteresis in soft lead zirconate titanate bulk ceramic

Dynamic ferroelectric hysteresis scaling of BaTiO3 single crystals