Investigating ferroelectric properties

The procedure to determine the scattering hysteresis is performed as follows An external field Ea is applied to the crystal along the polar axis for a duration of 10 seconds without illumination. Then the field is switched off. After a relaxation time of 1—2 minutes, which is long enough to reach the steady state of the spontaneous polarization in sbn [45], the crystal is illuminated with the pump beam. The asymmetric scattering pattern builds up and in accordance to the procedure shown above the spatial distribution of the scattered light is investigated in the steady state. 

9 Characterization of Polar Oxides by Photo-Induced Light Scattering 

In this section we show that photo-induced light scattering is a powerful tool, especially to obtain information about the polar structure in the crystal bulk. The polar structure in SBN Ce can be considered as the composition of different periodical and/or quasi-periodical assemblies of ferroelectric 180°-domains distributed in the bulk aligned along the c-axis. The existence of 

Such refractive index anomalies are built in along with the domain structure and remain unchanged if the crystal is not influenced externally, e.g., by thermal treatment, optical illumi- 

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PZN-PT, and YBa2Cug02 g. For the preparation of PZT thin films, the most frequently used precursors have been lead acetate and 2irconium and titanium alkoxides, especially the propoxides. Short-chain alcohols, such as methanol and propanol, have been used most often as solvents, although there have been several successful investigations of the preparation of PZT films from the methoxyethanol solvent system. The use of acetic acid as a solvent and chemical modifier has also been reported. Whereas PZT thin films with exceUent ferroelectric properties have been prepared by sol-gel deposition, there has been relatively Httle effort directed toward understanding solution chemistry effects on thin-film properties. 

Ferroelectric Thin-Film Devices. Since 1989, the study of ferroelectric thin films has been an area of increasing growth. The compositions studied most extensively are in the PZT/PLZT family, although BaTiO, KNbO, and relaxor ferroelectric materials, such as PMN and PZN, have also been investigated. Solution deposition is the most frequentiy utilized fabrication process, because of the lower initial capital investment cost, ease of film fabrication, and the excellent dielectric and ferroelectric properties that result. 

Investigation of the ferroelectric properties of oxyfluoride compounds is also a relatively new but fast-developing area in solid state chemistry [44-46]. 

Tantalum and niobium fluoride compounds that crystallize in coordination-type structures also seem to be perspective candidates for the investigation of ferroelectric properties. Ravez and Mogus-Milancovic [404] showed that some fluoride and oxyfluoride compounds with crystal structures similar to the Re03 type exhibit ferroelastic properties. For instance, ferroelastic properties were found in some solid solutions based on Nb02F and Ta02F [405,406]. 

In the growing field of applications for ferroelectric thin films it is of great interest to investigate the ferroelectric properties on a nanometer scale. A powerful tool for the monitoring and... 

Several members of the MM O3 class of ternary metal oxides adopt the perovskite-type (CaTiOs) structure and are sought as worthy target materials possessing ferroelectric properties see Ferroelectricity) Among the more widely investigated members of this class are BaTiOs and SrTiOs. Clearly, use of these materials as potential memory device... 

Transparent ferroelectric single crystals are traditionally used for electro-optic applications. Since the optical transparency was first discovered in lead-lanthanum-zirconate-titanate (PLZT), ferroelectric ceramics have been investigated in great depth such that, today, their characteristics allow them to compete with single crystals for certain electro-optic applications. The electro-optic properties of PLZT compositions are intimately related to their ferroelectric properties. Variations in ferroelectric polarization with an electric field, such as in a hysteresis loop, also affect the optical properties of the material. 

Flexible spacers in the semirigid-rod molecule allow the molecule to orient with order parameter greater than 0.8 when coated and cured upon a rubbed polyimide layer. Kinetics of the photo-polymerization [62,63] and surface-induced orientation [49] as well as mechanical [64,65], optical [59,66,67], and ferroelectric properties [68-70] of the anisotropic networks were thoroughly examined. These investigations were mainly carried out by the Philip s research group and were applied to develop liquid crystalline display devices [58,69]. 

The investigation of combined FLCPs was initiated by Zentel et al. [91-93] as a part of their approach to ferroelectric LC elastomers [94]. Figure 12 shows typical structures of combined FLCPs and cross-linkable chiral combined LC polymers. Poths et al. [67] used that approach to synthesize combined polymers with axially chiral mesogenic side groups (similar to the acrylic side-chain polymer above). The smectic C structure of polymers has been identified by optical microscopy and x-ray data, but no ferroelectric properties of the polymers have been reported yet. 

Piezoelectric/ferroelectric properties of Ln2Ti20y (Ln = La, Pr, Nd, or Sm) thin films were investigated at the nanoscale using a modified commercial atomic... 

Bayart, A., Saitzek, S., Chambrier, M.-H., Shao, Z., Ferri, A., Huv, M., Pouhet, R., Tebano, A., Roussel, P., and Desfeux, R. (2013) Microstructural investigations and nanoscale ferroelectric properties in lead-free Nd2Ti20y thin films grown on SrTiOs substrates by pulsed laser deposition. CrystEngComm, 15 (21), 4341-4350. 

Up to now the most extensively investigated chiral lyotropics are the chiral nematics (the historical but not appropriate term cholesteric is avoided in this chapter). The first evidence on this kind of mesophase has been reported by Radley and Saupe in 1978 [9]. Two studies on a lyotropic phase proposed to be analogous to the thermotropic Blue Phase have been published [10], one has been retracted [11] if there is any analogy, it is small. Blinov et al. reported on a nonaqueous chiral lamellar phase with ferroelectric properties experimental evidence for ferroelectricity in lyotropics is difficult to gain because of high electric conductivity and mostly nonuniform sample orientation. Nevertheless, the existence of piezoelectricity was interpreted as a manifestation of ferroelectricity [12]. 

Historically, nearly all the early investigations into the ferroelectric properties of PVDF were carried out on thin ( 25 jam) films. This was necessary for very good reasons. Most importantly, the material must be oriented to develop an incipient ferroelectric structure. This is most conveniently done by using conventional thin film making equipment, which stretches a preformed polymer strip in either one or two in-plane directions. In addition to this requirement, very high fields (typically 100 kV mm ) must be applied to the oriented polymer during the poling... 

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