Free-defects samples

As follows from the adduced data, the good correspondence of f and is obtained, particularly taking into account low precision of determination in this strains range. Besides, the theoretical calculation gives the greatest Ej. value for free-defects samples that in practice is achieved with difficulty, particularly for brittle polymers. Therefore, for the data of Fig. 7.6 the ex-T... 

The problem of the structural multidomaining below Ta makes it difficult to reach a definite conclusion, as shown in Figs. 5 and 13. Measurements for defect-free and stress-free STO samples are indispensable for a definite conclusion about the symmetry of the ferroelectric phase of STO 18. Finally, we can conclude that STO 18 may be a typical soft mode ferroelectric. 

This method is fast, precise, and repeatable. Results are httle affected by fillers. A major drawback is that it requires a relatively large, flat, defect-free isotropic sample, rendering it inapplicable to most fabricated items. Some degree of exactitude is inevitably lost in the calibration process, so the absolute precision and accuracy of the degree of ciystallinity is somewhat lower than that of the flotation method against which it is calibrated. 

These equations reveal that sample dimensions must also be known with precision, and, of course, the specimens must be free from defects. 

Static defects scatter elastically the charge carriers. Electrons do not loose memory of the phase contained in their wave function and thus propagate through the sample in a coherent way. By contrast, electron-phonon or electron-electron collisions are inelastic and generally destroy the phase coherence. The resulting inelastic mean free path, Li , which is the distance that an electron travels between two inelastic collisions, is generally equal to the phase coherence length, the distance that an electron travels before its initial phase is destroyed ... 

It is well know that the zeolite materials synthesized in alkaline systems usually have a high number of silanol groups (=SiOH) named defect groups [10] which possess a moderated Bronsted acidity [11]. Oppositely, Silicalite-1 synthesized in fluorine media are relatively defect-free [12] and the fluorine ions remain in the small cages of the MFI structure even after the calcination process [12]. The 29Si-NMR analyses carried out on samples Na-Silicalite-1 and F-Silicalite-1 confirm the presence of silanol groups only on the SI support surface (results not showed). Delaminated zeolites (ITQ-6) are obtained by exfoliation of as-synthesized lamellar precursor zeolites [13]. After this process, the final structure of the delaminated zeolite results in a completely hydroxylated and well-ordered external surface [13]. 

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