Temperature of Selected Ferroelectric Crystals

CURIE TEMPERATURE OF SELECTED FERROELECTRIC CRYSTALS (continued)... 

Useful applications have been found lor the varied effects of these crystal changes. One of the first came from the properly of selectively reflecting visible light because this is lempcraiurv-dependent. the property can be used as a temperature detector, and in gel lurm liquid crystals have been used lor the early detection of those cancers which cause hot spots in the body. Applications of the smectic modifications arise from their ferroelectric properties this phase can function as a fast-switching light-valve device with memory. This kind of application requires some... 

Studying the temperature evolution of UV Raman spectra was demonstrated to be an effective approach to determine the ferroelectric phase transition temperature in ferroelectric ultrathin films and superlattices, which is a critical but challenging step for understanding ferroelectricity in nanoscale systems. The T. determination from Raman data is based on the above mentioned fact that perovskite-type crystals have no first order Raman active modes in paraelectric phase. Therefore, Raman intensities of the ferroelectric superlattice or thin film phonons decrease as the temperature approaches Tc from below and disappear upon ti ansition into paraelectric phase. Above Tc, the spectra contain only the second-order features, as expected from the symmetry selection rules. This method was applied to study phase transitions in BaTiOs/SrTiOs superlattices. Figure 21.3 shows the temperature evolution of Raman spectra for two BaTiOs/SrTiOa superlattices. From the shapes and positions of the BaTiOs lines it follows that the BaTiOs layers remain in ferroelectric tetragonal... 

In the present work, to find the experimental evidence for preferential dipole orientation during electrospinning, the P(VDF-TrFE) copolymer was selected instead of PVDF as it has a definite Curie transition temperature (T ) and orJy one ferroelectric crystalline stmcture (P-phase) at ambient temperature far below On the other hand, PVDF has at least four crystal modifications at ambient temperature depending on sample preparation methods [1], which makes it much more difficult to find experimental evidence of dipole orientation during electrospinning using... 

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