“…Therefore one can expect that the variation of the 2 nd harmonic PFM signal reflects the temperature dependence of the local dielectric permittivity. Indeed, we observed a sharp maximum of the 2 nd harmonic PFM signal close to the Curie temperature of the polymer matrix and its temperature dependence is qualitatively similar to the temperature dependence of the high-frequency dielectric permittivity for this compound 27 .Figure 4Temperature dependences of the 1 st harmonic (piezoresponse) ( a ) and the 2 nd harmonic ( b ) of the PFM signal measured inside the poled area.
…”
Polarized states of polymer/inorganic inclusion P(VDF-TrFE)-(Pb,Ba)(Zr,Ti)O3 composites are studied at the nanoscale using both piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM). It has been shown that inorganic inclusions can be visualized using KPFM due to a discontinuity of the surface potential and polarization at the interface between the inclusions and the polymer matrix. The temperature evolution of the PFM and KPFM signal profiles is investigated. Softening of the polymer matrix on approaching the Curie temperature limits application of the contact PFM method. However non-contact KPFM can be used to probe evolution of the polarization at the phase transition. Mechanisms of the KPFM contrast formation are discussed.
“…Therefore one can expect that the variation of the 2 nd harmonic PFM signal reflects the temperature dependence of the local dielectric permittivity. Indeed, we observed a sharp maximum of the 2 nd harmonic PFM signal close to the Curie temperature of the polymer matrix and its temperature dependence is qualitatively similar to the temperature dependence of the high-frequency dielectric permittivity for this compound 27 .Figure 4Temperature dependences of the 1 st harmonic (piezoresponse) ( a ) and the 2 nd harmonic ( b ) of the PFM signal measured inside the poled area.
…”
Polarized states of polymer/inorganic inclusion P(VDF-TrFE)-(Pb,Ba)(Zr,Ti)O3 composites are studied at the nanoscale using both piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM). It has been shown that inorganic inclusions can be visualized using KPFM due to a discontinuity of the surface potential and polarization at the interface between the inclusions and the polymer matrix. The temperature evolution of the PFM and KPFM signal profiles is investigated. Softening of the polymer matrix on approaching the Curie temperature limits application of the contact PFM method. However non-contact KPFM can be used to probe evolution of the polarization at the phase transition. Mechanisms of the KPFM contrast formation are discussed.
“…These results are consistent with those presented elsewhere and can be explained by the existence of an intermediate polar γ or non‐polar ɛ phase, probably, of orthorhombic conformation . The γ phase has a conformation in between that of the α (paraelectric) and β (ferroelectric) phases and is hardly experimentally accessible , although it may serve in precedence of the main ferroelectric phase on cooling . Another explanation was proposed by R. Gregorio et al considering the existence of two types of paraelectric and ferroelectric phases with different Curie temperatures.…”
Section: Resultssupporting
confidence: 91%
“…a), was discussed when explaining Fig. a . Moreover, every cycle below 390 K shifts the peaks more down (dashed lines in Fig.…”
Section: Resultsmentioning
confidence: 87%
“…The complex dielectric permittivity was measured as a function of frequency (20 Hz – 1 MHz) and temperature (300 K – 415 K). A more detailed description of ultrasonic and dielectric measurements can be found elsewhere .…”
Section: Methodsmentioning
confidence: 99%
“…During the last decades several groups have reported on the effect of annealing and thermal cycling on properties of P(VDF‐TrFE) . This makes interesting to carry out investigations of the polymer based composites with various compositions of CNT fillers . It is the purpose of the present article to report on detailed investigations of the effect of thermal cycling and annealing on ferroelectric phase transition, ultrasonic, and dielectric properties of P(VDF‐TrFE)/CNT composites.…”
Broadband dielectric properties of tungsten disulfide (WS 2 ) nanotubes/polyurethane (PU) composites over a wide temperature range (300 K-450 K) are presented for concentrations up to 2 wt%. Although no electrical percolation was observed in composites, at room temperature the dielectric permittivity of thermosetting composites with 2 wt% inclusions is 2 times higher than the dielectric permittivity of the pure polymer, that indicate that the composites are suitable for antistatic applications. Broadband dielectric properties of the composites are mainly governed by the a relaxation, the dynamics of the "soft" molecular segment of the PU chain. The Vogel temperature decreases with increase in the concentration of the WS 2 nanotubes. At higher temperatures (above 380 K) the electrical conductivity dominates in properties of pure PU and composites with the WS 2 inclusions as well. The DC conductivity increases with the WS 2 concentration in thermosetting composites, while its activation energy is almost independent from the WS 2 concentration far from melting point. The DC conductivity has some change in slope close to 420 K. Above room temperature, the large ultrasonic relaxational attenuation maxima and the velocity dispersion were observed. It was found that the attenuation peak in composites shifted to lower temperatures after addition of nanoparticles. The ultrasonic attenuation data of thermosetting composites were fitted to the relaxation equation with the single temperature-dependent relaxation time. The thermal activation energy of the relaxation process, which was calculated from the ultrasonic data, was found to increase in PU with the concentration of WS 2 nanotubes. POLYM. COMPOS., 00:000-000,
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