Orientational domain

Region III, IV the late stage of SD, i.e., the process where the oriented domains grow with self-similarity. The reason for the time dependences of the integrated intensity is unclear. 

Fig. 31 Structural formation model for the initial stage of polymer crystallization [19], N G nucleation and growth of oriented domains, SD spinodal decomposition into oriented and unoriented domains, Tb, Ts, and Tx bimodal, spinodal, and crystallization temperatures, respectively I isotropic, N smectic, and C crystalline...

Unlike the bulk morphology, block copolymer thin films are often characterized by thickness-dependent highly oriented domains, as a result of surface and interfacial energy minimization [115,116]. For example, in the simplest composition-symmetric (ID lamellae) coil-coil thin films, the overall trend when t>Lo is for the lamellae to be oriented parallel to the plane of the film [115]. Under symmetric boundary conditions, frustration cannot be avoided if t is not commensurate with L0 in a confined film and the lamellar period deviates from the bulk value by compressing the chain conformation [117]. Under asymmetric boundary conditions, an incomplete top layer composed of islands and holes of height Lo forms as in the incommensurate case [118]. However, it has also been observed that microdomains can reorient such that they are perpendicular to the surface [ 119], or they can take mixed orientations to relieve the constraint [66]. 

In a small ( 100 A) region, the 22 X., 3 reconstruction is uniaxial. The ridge runs in one direction. However, the gold surface has threefold symmetry (p3ml). On a large area, the reconstruction should run in three directions 120° apart with equal probability. Between regions with different reconstruction orientations, domain boundaries should be observed. While no scattering method may provide detailed information about these domain boundaries, STM may. 

Figure 32 (a) Examples of satellites observed in [0011 E D. patterns of PbBaYSrCuaO, [3,1] phase (b) the extra spots are dearly visible when the zone is slightly deviated from the exact orientation (c) schematic representation of the pattern, two sets of satellites are visible they are characteristic of 90" oriented domains basic spots at level 1/2 are represented as open circles, systems 1 and 2 (4 x dii()),. systems 3 and 4 (6 x d110). 

Polarization of a ferroelectric material varies nonlinearly with the applied electric field. The P-E behaviour is characterized by a hysteresis loop and observation of the hysteresis loop is the best evidence for the existence of ferroelectrcity in a material. The hysteresis loop has its origin in the rearrangement of domains under the influence of an applied elecric field. Generally, the domains are randomly distributed, giving a net zero polarization. Under an applied field or mechanical stress, favourably oriented domains... 

Fig. 4.13 (a) Field ion image of an ordered PtCo alloy. Co atoms do not give rise to image spots, thus only the Pt sublattice is imaged. The circular area near the center of the image is a thick layer of 90° orientation domain. (b) Field ion image of an ordered Ni4Mo where Ni atoms cither are invisible or appear much dimmer. 

Fig. 9 (a) Sketch of the structure of the hexagonal columnar phase of DNA, showing parallel molecules hexagonally packed in the plane perpendicular to their axis, a and 4 are the lattice parameters, (b) COL developable domains observed in polarized microscopy, w indicates defect walls between differently oriented domains, while 7t stands for point defect around which DNA molecules continuously bend (size bar is 10 pm). Adapted with permission from [27]... 

Magnetization of a material. Initially, magnetization increases by growth of favorably oriented domains. At high fields, the direction of magnetization rotates out of the easy direction. 

Domain wall polarization plays a decisive role in ferroelectric materials and contributes to the overall dielectric response. The motion of a domain wall that separates regions of different oriented polarization takes place by the fact that favored oriented domains with respect to the applied field tends to grow. 

For example, Wakayama and coworkers discovered the formation of two oppositely orientated domains of 5,10,15,20- lclrakis(3,5-di-ferf-bulylphcnyl)-porphine deposited onto a Cu surface using low-temperature scanning tunneling microscopy [124]. It was demonstrated that the twin domains were produced by a pair of chiral conformations induced by a combination of symmetrical tilting and twisting rotation of the phenyl rings with respect to... 

It should be noted that a poling process is often necessary with single-crystal ferroelectric bodies because they contain a multiplicity of randomly oriented domains. There is therefore a sequence of states of increasing orderliness polycrystalline ferroelectric ceramics, poled ferroelectric ceramics, single-crystal ferroelectrics and single-domain single crystals. 

As a ferroelectric perovskite in ceramic form cools through its Curie point it contracts isotropically since the orientations of its component crystals are random. However, the individual crystals will have a tendency to assume the anisotropic shapes required by the orientation of their crystal axes. This tendency will be counteracted by the isotropic contraction of the cavities they occupy. As a consequence a complex system of differently oriented domains that minimizes the elastic strain energy within the crystals will become established. 

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