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Current Trends for Actuators and Micromechatronics
Published in Kenji Uchino, Micro Mechatronics, 2019
Copolymers from the system polyvinylidene difluoride-trifluoroethylene [P(VDF-TrFE)] are also known as piezoelectric materials. The strain induced in these materials is not very large, however, due to a very high coercive field. An electron irradiation treatment has been applied to materials from this system by Zhang et al. that significantly enhances the magnitude of the induced strain.25 A 68/32 mole percent P(VDF-TrFE) copolymer film is irradiated by a 1.0-MeV electron beam at 105°C. The 70 Mrad exposure results in a diffuse phase transition and a decrease in the transition temperature, as compared with the nonirradiated material. It is believed that the observed changes in the phase transition are due to the development of a microdomain state, similar to that associated with relaxor ferroelectrics, which effectively interrupts the long-range coupling of ferroelectric domains. The strain curve pictured in Figure 1.30b for an irradiated P(VDF-TrFE) specimen demonstrates that induced strains as high as 5% are possible with an applied field strength of 150 MV/m. Note again that the longitudinal strain is negative.
Foundations of Piezoelectrics
Published in Kenji Uchino, High-Power Piezoelectrics and Loss Mechanisms, 2020
Relaxor ferroelectrics can be prepared either in polycrystalline form or as single crystals. Different from the previously mentioned normal ferroelectrics such as BT and PZT, relaxor ferroelectrics exhibit a broad phase transition from the paraelectric to ferroelectric state, a strong frequency dependence of the dielectric constant (i.e., dielectric relaxation) and a weak remnant polarization. Lead-based relaxor materials have complex disordered perovskite structures.
Review of Piezoelectricity and Magnetostriction
Published in Kenji Uchino, FEM and Micromechatronics with ATILA Software, 2018
Relaxor ferroelectrics can be prepared either in polycrystalline form or as single crystals. They differ from the previously mentioned normal ferroelectrics in that they exhibit a broad phase transition from the paraelectric to ferroelectric state, a strong frequency dependence of the dielectric constant (i.e., dielectric relaxation), and a weak residual polarization. Lead-based relaxor materials have complex, disordered perovskite structures.
Phenomenological theory of phase transitions in the MPB region of (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystals
Published in Phase Transitions, 2020
Kum-Ok Jang, Il-Hwan Kim, Il-Hun Kim, Sok-Gil Im, Kye-Ryong Sin, Chol-Jin Kim
The ultrahigh strain(>1.7%), superior high electromechanical coupling factor(k33 > 90%) and very large piezoelectric coefficient(d33 > 2500pC/N) observed experimentally in the Morphotropic Phase Boundary(MPB) regions of the relaxor ferroelectric (1−x)Pb(Mg1/3Nb2/3)O3-xPbTiO3(PMN-PT) and (1−x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) solid solution systems are excellent as compared with conventional piezo/ferroelectric materials such as BaTiO3, KNbO3 and PbZr1−xTixO3(PZT) which have been widely used for more than 60 years in the field of piezoelectric material [1]. From this these relaxor ferroelectrics have been applied to various sensors, transducers and actuators, and have been also regarded as promising materials for new generations of high performance electromechanical devices [1]. Thus, how the crystal structures and dielectric and piezoelectric properties in PMN-PT and PZN-PT single crystals change with the composition, temperature and electric field has been studied widely [1–9]. Among PZT, PMN-PT and PZN-PT with very large piezoelectric effect in the MPB regions, PMN-PT is especially interesting, as it can be easily prepared both in single crystal and in ceramic forms, whereas it is difficult to prepare PZT single crystals and PZN–PT ceramics [1,10].
Accounting for Location Measurement Error in Imaging Data With Application to Atomic Resolution Images of Crystalline Materials
Published in Technometrics, 2022
Matthew J. Miller, Matthew J. Cabral, Elizabeth C. Dickey, James M. LeBeau, Brian J. Reich
Knowing the relationships between local chemistry and structure can help guide the optimization of composition to maximize properties, such as piezoelectricity, an important property present in relaxor ferroelectric materials. While the composition can be empirically iterated until an optimum is reached, access to the underlying structural information is invaluable to gain rational control over the design process. For example, such relationships can suggest target compositions or the introduction of alternative elements that can introduce a stronger correlation.
Temperature dependence on ferroelectric properties and strain performance of PLZT ceramics containing 9 mol% La
Published in Phase Transitions, 2020
Narit Funsueb, Apichart Limpichaipanit, Athipong Ngamjarurojana
La-modified PZT or PLZT ceramics possess high dielectric and piezoelectric properties compared to the pure PZT system because of the donor effect. When replacing divalent Pb2+ ions with trivalent La3+ ions, the vacancies at B site of the perovskite structure (ABO3) are generated [3, 5]. Normally, the typical chemical formula of PLZT ceramics is (Pb1-y Lay)(Zrx, Ti1-x) 1-0.25y VB0.25y O3 where y is the amount of La and VB is the concentration of vacancy at B site. PLZT ceramics also have electric domain structure and they are more mobile compared to pure PZT as a result of soft doping. Domain wall and dipole can move under an applied electric field, resulting in induced strain and polarization [6]. The ferroelectric properties can be divided in two types as normal ferroelectric and relaxor ferroelectric. Normal ferroelectric shows sharp peak phase transition at the Curie temperature which is not dependent on frequency. Induced strain and polarization can be seen as a slim loop and strain loop shows quadratic relation. Relaxor ferroelectrics include the contribution of polarnanoregions (PNRs) from disordered structure and domain wall movement, which gives rise to a complex nonlinear (diffusion as maximum dielectric constant depends on frequency) and hysteresis behavior with the characteristic electric induced strain loop so-called a butterfly-like shape. The decrease of Zr/Ti ratio in PLZT ceramics changes the crystal structure from rhombohdral to morphotropic phase boundary (MPB) and tetragonal structure, respectively. MPB enhances material properties and behavior under applied electric fields or temperature variations. The remnant polarization, coercive field, shape of the hysteresis loop, dielectric and piezoelectric properties depend on degree of freedom and domain wall mobilities caused by the Zr/Ti ratio [7–9].