Defect-stabilized phases

The presence, and to some degree the discovery, of TGB phases in liquid-crystalline systems stems from theoretical studies by de Gennes [18], Through modeling of the N-A transition, de Gennes predicted that, for a second order nematic to smectic A phase transition, a defect stabilized phase could occur... 

Cation vacancies and interstitials, (111) twins and stacking faults, grain boundaries, microstrains, misfit dislocation network at C03O4/C0O interface Dislocations and (100) stacking faults intergrowth of e and P phases. Cations vacancies and superstructure (110) stacking faults and twins Clusters of point defects (110) twins surface steps, dislocations, spinel microinclusions, planar defects stabilized by impurities. 

The doping of Zr02 with alkaline earth metal cations (A ) is less effective due to a greater tendency to defect association and to a lower thermodynamic stability of the cubic fluorite-type solid solutions in Zr02-A0 systems. To date, attempts to increase the stability of Sc-containing materials by codoping, or to reduce the cost of Ln -stabilized phases by mixing them with cheaper alkaline earth dopants, have not yielded any worthwhile results [228]. 

C in the absence of external stress (0 MPa) is released the segment mobility in macromolecules, which is a precondition for the cold crystallization. For similar structures the applied stress of 3 MPa at temperature of 80 "C is not enough to cause noticeable fibers orientation and structure stabilization. The melting peaks of these samples are broader and imperfect because the melting polymer system is imperfect, contains less and more defective crystalline phase. 

The most developed and widely used approach to electroporation and membrane rupture views pore formation as a result of large nonlinear fluctuations, rather than loss of stability for small (linear) fluctuations. This theory of electroporation has been intensively reviewed [68-70], and we will discuss it only briefly. The approach is similar to the theory of crystal defect formation or to the phenomenology of nucleation in first-order phase transitions. The idea of applying this approach to pore formation in bimolecular free films can be traced back to the work of Deryagin and Gutop [71]. 

The parent structure of the anion-deficient fluorite structure phases is the cubic fluorite structure (Fig. 4.7). As in the case of the anion-excess fluorite-related phases, diffraction patterns from typical samples reveals that the defect structure is complex, and the true defect structure is still far from resolved for even the most studied materials. For example, in one of the best known of these, yttria-stabilized zirconia, early studies were interpreted as suggesting that the anions around vacancies were displaced along < 111 > to form local clusters, rather as in the Willis 2 2 2 cluster described in the previous section, Recently, the structure has been described in terms of anion modulation (Section 4.10). In addition, simulations indicate that oxygen vacancies prefer to be located as second nearest neighbors to Y3+ dopant ions, to form triangular clusters (Fig. 4.11). Note that these suggestions are not... 

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