Ferroelectric relaxor

Key Words Dipolar glasses, Ferroelectric relaxors, Conducting polymers, NMR line shape, Disorder, Local polarization related to the line shape, Symmetric/asymmetric quadrupole-perturbed NMR, H-bonded systems, Spin-lattice relaxation, Edwards-Anderson order parameter, Dimensionality of conduction, Proton, Deuteron tunnelling. 

PbSci/2Nbi/203 45Sc,93Nb,207Pb SC, ferroelectric relaxor, local method necessary 253,254... 

Shrout, T. R., and Halliyal, A., Preparation of lead-based ferroelectric relaxors for capacitors, Am. Ceram. Bull., 66, 704 (1987). 

Fig. 1.4 The alpha and beta phases of the ferroelectric polymer PVDF. The beta phase is stable at room temperature but can be reversibly changed to the alpha phase by heating above the Curie temperature. Above the Curie temperature, an electric field can be used to induce a change between the alpha and beta phases. For ferroelectric relaxor polymers, the Curie temperature is below room temperature so the alpha phase is stable. A change to the beta phase can be induced by an electric field [7], Materials Today 2007, reprinted with permission...

Recent work by Bao et al. has shown that P(VDF-TrFE) synthesized via reductive dechlorination from P(VDF-CTFE) exhibits ferroelectric relaxor behavior at high temperature ( 100°C) with a melting point near 200°C [111]. This result is important as it provides another avenue to study the relaxor phenomena which are still not completely understood. The high melting point coupled with the high dielectric response of these materials at high temperature makes them attractive for use in high-temperature capacitors. 

Bao HM, Jia CL, Wang CC, Shen QD, Yang CZ, Zhang QM (2008) A type of poly(vinylidene fluoride-trifluoroethylene) copolymer exhibiting ferroelectric relaxor behavior at high temperature (similar to 100°C). Appl Phys Lett 92 042903... 

Science for Materials in the Frontier of Centuries Advantages and Challenges, International Conference, Kyiv, Ukraine, Nov. 4-8,2002, Vol. 1, ed. V.V. Skorokhod, Frantsevich Institute for Problems of Materials Science of National Academy of Science of Ukraine, Kiev, Ukraine, 2002 R 300 M.D. Glinchuk, V.V. Laguta and l.P. Bykov, New Generation of the Materials for Sensors, Actuators and Ultrasound Technique on the Base of Ferroelectric Relaxors , p. 28... 

Zhang, S., Li, F., 2012. High performance ferroelectric relaxor-PbXi03 single crystals status and perspective. J.Appl. Phys. Ill,031301. 

Glinchuk, M.D., Farhi, R. A random field theory based model for ferroelectric relaxors. J. Phys. Condens. Matter 8,6985-6996 (1996)... 

Since the relaxors attract much attention of scientists and engineers due to their usefulness for applications (see Sect. 1.3.4), the ferroelectric relaxor films... 

The hysteresis loops studies appear to be very informative for nanograin ceramics also. In particular, above we have discussed above the relaxor state induced by the grain sizes. The studies of the relaxor state have been made on the basis of dielectric response analysis. In Ref. [27], the additional firm evidence of relaxor state has been obtained with the help of hysteresis loops measurements. In Fig. 2.16 we report the shape of hysteresis loops in ferroelectric relaxors at different temperatures. It is seen, that at r > (Tm = 363 K is the temperature of dielectric permittivity maximum for PbSci/2Nbi/202 (PSN)) there is no residual polarization, while it is nonzero at T< r. Similar behavior has been observed for 730 nm thick Pbo.76Cao.24Ti03 (PCT) film with average grain sizes 86 nm and Tm = 553 K. 

Uesu, Y., Yamada, Y, Fujishiro, K., Tazawa, H., Enokido, S., Kiat, J.-M., and Dkhil, B. (1998) Stmctural and optical studies of development of the long-range order in ferroelectric relaxor Pb(Zn] 3Nb2/3)03-PbTi03. Ferroelectrics, 217, 319-325. 

Kutnjak Z, Petzelt J, Blinc R (2006) The giant electromechanical response in ferroelectric relaxors as a critical phenomenon. Nature 441 956-959... 

On the other hand, the A positions can be shared by dissimilar ions such as Na and Bi, yielding the complex ferroelectric relaxor ceramic BNT (bismuth sodium titanate) (Hosono et al., 2001 Pookmanee et al., 2001 Pookmanee et al, 2003 see Section 8.3.3). 

Figure 8.17 Temperature dependence of the polarization in classic ferroelectric (a) and ferroelectric relaxor ceramics (b). To Curie temperature Tr Burns temperature.

More detailed recent information on ferroelectric relaxor ceramics can be obtained from Ye (2008). Lead-free BaFeo.5Nbo.5O3 ceramics with multiferroic properties were developed by Bochenek et al. (2009). 

Zhang, Q.M., Bharti, V., Zhao, X. Giant electrostrictive response and ferroelectric relaxor baehavior in electron irradiated polyvinyUdene fluoride-trifiuoroethylene polymer. Science 280, 2101-2104 (1998)... 

The increased strain with increasing dc bias in figure 7 can be explained by previous dielectric measurements of PLZT (9.0/65/35) ceramics as a function of both tempierature and dc bias (Bobnar et al. 1999) They have observed a sharp increase in the dielectric permittivity with increasing dc bias fields at temperatures dose to the ferroelectric-relaxor phase transition, indicating that the dc bias is inducing the creation of electric dipoles at this transition, and hence increasing the overall piezoelectric response. 

Fig. 8 (top) Cross-sectional view of a transparent multilayered ferroelectric relaxor film vibrator under a cover with capacitive touch sensitive layers, (bottom) Photograph of a tactile-feedback touch screen with a single layer P(VDF-TrFE-CTFE) vibrator (Reprinted with permission (Ju et al. 2014))... 

Lead magnesium niobate, Pb(Mg 3Nb2/3)03, is a ferroelectric relaxor material which is paraelectric at room temperature. The perovskite phase is typically modifield with addition of lead titanate or barium titanate, which raises the Curie temperature to near room temperature. Very high dielectric constants can be achieved, >20,000, but at the expense of temperature stability. 

Sekar, M.M.A. (1994) Combustion synthesis and properties of ferroelectrics, relaxor ferroeleclrics and microwave resonator materials, PhD Thesis, Indian Institute of Science, Bangalore. 

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