Films of semicrystalline poly(vinylidene fluoride) (PVDF) in the βphase were studied by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The main goal of this study was to improve the understanding of the structural changes that occur in β-PVDF during a mechanical deformation process. FTIR spectroscopy was used to examine the structural variations as a function of strain. DSC data allowed measurement of the melting temperatures and enthalpies of the material before and after deformation, providing information about the changes in the crystalline fraction. After the molecular vibrations were assigned to the corresponding vibrational modes, we investigated the energy and intensity variations of these vibrations at different deformations. A reorientation of the chains from perpendicular to parallel to the stress direction was observed to occur in the plastic region. During the deformation, a decrease in the degree of crystallinity of the material was observed, but the thickness of the lamellae did not change significantly.

No abstract

No abstract

Comment on "Complete sets of elastic, dielectric, and piezoelectric properties of flux-grown [011]-poled Pb (Mg 1 / 3 Nb 2 / 3) O 3 − (28-32) % PbTiO 3 single crystals" [Appl.

A cubic-tetragonal-trigonal sequence of phase transitions in the relaxor ferroelectric Na& &~Bi &~& Ti03 (NBT) has been studied by Brillouin scattering. Pronounced anomalies for both the hypersonic velocity and damping have been found that peak just between two phase transitions in contrast to the ordinary well-known behavior with anomalies in the vicinity of every transition point. The fact that these anomalies are centered in the intertransition region and extend beyond both transitions is attributed to the fluctuations of two coupled order parameters associated with disorder in the Naand Bi-cation distribution in a manner characteristic of relaxor ferroelectrics. Such a phenomenon seems to be typical of relaxor materials and to be the basis of the difFuse phase-transition dynamics.