Second ferroelectrics

Fischer, E.V. Proceedings of the Second Ferroelectric Liquid Crystal Conference at Goteborg, Sweden (June 1989), Ferroelectrics in press ... 

In addition to dealing with magnetic ceramics, this chapter also deals with dielectric ceramics, such as ferroelectrics, for which the dielectric response is nonlinear. Ferroelectricity was first discovered in 1921 during the investigation of anomalous behavior of Rochelle salt. A second ferroelectric material was not found until 1935. The third major ferroelectric material, BaTi03, was reported in 1944. Ferroelectric ceramics possess... 

A related phenomenon with electric dipoles is ferroelectricity where there is long-range ordermg (nonzero values of the polarization P even at zero electric field E) below a second-order transition at a kind of critical temperature. 

Smolyaninov I P, Zayats A V and Davis C C 1997 Near-field second-harmonic imaging of ferromagnetic and ferroelectric materials Opt. Lett. 22 1592-4... 

In the single-domain state, many ferroelectric crystals also exhibit high optical nonlinearity and this, coupled with the large standing optical anisotropies (birefringences) that are often available, makes the ferroelectrics interesting candidates for phase-matched optical second harmonic generation (SHG). 

In this chapter studies of physical effects within the elastic deformation range were extended into stress regions where there are substantial contributions to physical processes from both elastic and inelastic deformation. Those studies include the piezoelectric responses of the piezoelectric crystals, quartz and lithium niobate, similar work on the piezoelectric polymer PVDF, ferroelectric solids, and ferromagnetic alloys which exhibit second- and first-order phase transformations. The resistance of metals has been investigated along with the distinctive shock phenomenon, shock-induced polarization. 

The second group is the group of oxyfluorides that are derived from ferroelectric oxides by means of fluorine-oxygen substitution. The basic oxides are usually perovskite, tetragonal tungsten bronze, pyrochlore, lithium tantalate etc. [400]. 

A.I. Agulyansky, Yu.I. Balabanov, V.Ya. Kuznetzov, L.A. Agulyansky, Proceedings of the second conference on phys. - chem. Fundamentals of ferroelectrics and related materials, Nauka, Moscow, 1983, p.85. 

Two other important points have to be stressed. The first is that above Tc = 210 K, T2 does not depend on the frequency offset so that the nanocluster dynamics is similar in different parts of the crystal. Below Tc, on the other hand, T2 depends on the frequency offset and the nanocluster dynamics is different in different parts of the crystal, as expected for a two-component system consisting of ferroelectric regions and a spherical glass-type matrix. The second point is that in the FC T2 data around 140-150 K, a second flat T2... 

Figure 6 shows the influence of the pressure of e T) on both ST018-92(a) and SCT(0.007) [21]. We first note the large shift in the transition to lower temperature for STO 18. The initial slope is dTcdP = - 20 K/kbar, a large effect. Second, there is a large decrease in the ampHtude of the peak with pressure. At 0.70 kbar, the transition is completely suppressed, and the e (T) response closely resembles that of STO 16 at 1 bar. These pressure effects are characteristic of displacive ferroelectrics in the quantum regime and can be understood in terms of the soft-mode theory. The situation is similar for SCT(0.007), as shown in Fig. 6b. In the case of SCT(0.007), ferroelectricity completely disappears at 0.5 kbar.

This energy has minima at /x = /Xs. where yxs is a saturated dipole value, so that the saturated force has a value Fg = 2KfZg. The frequency of small-amplitude ferroelectric mode, where all dipoles vibrate in phase around fig, is given by twpE = /mY, where is the second derivative of... 

The critical point is one of many examples of higher-order phase transitions including the second-order transitions in ferromagnetics and ferroelectrics and A-transition in liquid He. Unlike the first-order transition, the heat of the... 

FLC phases in the surface stabilized geometry possess a single C2 axis of symmetry, and therefore polar order and non-zero x<2) in the simple electronic dipolar model. Thus, it is not surprising that experiments aimed at measuring this property were first reported shortly after the Clark-Lagerwall invention. Early studies (14-15) described second harmonic generation in (S)-2-Methylbutyl 4-(4-decyloxybenzylideneamino)cin-namate, the first ferroelectric liquid crystal, also known as DOBAMBC (1). 

The supramolecular structure of block co-polymers allows the design of useful materials properties such as polarity leading to potential applications as second-order nonlinear optical materials, as well as piezo-, pyro-, and ferroelectricity. It is possible to prepare polar superlattices by mixing (blending) a 1 1 ratio of a polystyrene)-6-poly(butadiene)-6-poly-(tert-butyl methacrylate) triblock copolymer (SBT) and a poly (styrene)-Apoly (tert-butyl methacrylate) diblock copolymer (st). The result is a polar, lamellar material with a domain spacing of about 60 nm, Figure 14.10. 

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