Non-linear dielectric spectroscopy for detecting and evaluating structure-property relations in a P(VDF-TrFE-CFE) relaxor-ferroelectric terpolymer

Non-linear dielectric spectroscopy (NLDS) is employed as an effective tool to study relaxation processes and phase transitions of a poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) relaxor-ferroelectric (R-F) terpolymer in detail. Measurements of the non-linear dielectric permittivity $${\varepsilon _{2}^{'}}$$ ε 2 ′ reveal peaks at 30 and 80$$\,^\circ$$ ∘ C that cannot be identified in conventional dielectric spectroscopy. By combining the results from NLDS experiments with those from other techniques such as thermally stimulated depolarization and dielectric-hysteresis studies, it is possible to explain the processes behind the additional peaks. The former peak, which is associated with the mid-temperature transition, is found in all other vinylidene fluoride-based polymers and may help to understand the non-zero $$\varepsilon _\mathrm {2}^{'}$$ ε 2 ′ values that are detected on the paraelectric phase of the terpolymer. The latter peak can also be observed during cooling of P(VDF-TrFE) copolymer samples at 100$$\,^\circ$$ ∘ C and is due to conduction and space-charge polarization as a result of the accumulation of real charges at the electrode–sample interface.

SPECTRA OF THERMOSTIMULATED DEPOLARIZATION OF BIOCOMPOSITES WITH FILLERS OF BIOLOGICAL ORIGIN

The paper presents the results of studying the spectra of thermally stimulated depolarization of high-pressure polyethylene modified with fillers of biocomposites with fillers of biological origin - fish bone and fish scales. It was revealed that the stability and surface density of space charges can be controlled by varying the volumetric content of biological fillers. The optimal values of bio-fillers that contribute to the stability of the surface density of the studied biocomposites have been determined.

EFFECT OF TEMPERATURE TREATMENT ON THE ENERGY SPECTRUM OF DEFECTS IN SILICON DOPED WITH MOLYBDENUM

The paper presents the results of studying the spectra of thermally stimulated depolarization of high-pressure polyethylene modified with fillers of biocomposites with fillers of biological origin - fish bone and fish scales. It was found that the stability and surface density of space charges can be controlled by varying the volumetric content of biological fillers. The optimal values of bio-fillers that contribute to the stability of the surface density of the investigated biocomposites have been determined.

Исследование диэлектрического отклика, проводимости и тока термостимулированной деполяризации в релаксорном сегнетоэлектрике PbNi-=SUB=-1/3-=/SUB=-Nb-=SUB=-2/3-=/SUB=-O-=SUB=-3-=/SUB=-

This paper presents results of a study of temperature dependences of dielectric response and DC and AC - conductivity in single crystals of the relaxor ferroelectric PbNi1/3Nb2/3O3 (PNN) in a wide range of frequencies (10 Hz - 100 kHz) and temperatures (80 - 750 K). Anomalies in the dielectric response in the form of broad frequency-dependent maxima in the vicinity of 153 and 730 K are observed. The thermal activation character of DC conductivity has been obtained, and activation energies determined as Ea = 770 meV (T > 310 K) and Ea = 23 meV (T <310 K). The analysis of conductivity gives reason to assume the existence of local conductivity in the low-temperature region. It is shown that the conductivity character changes above 350 K from the local to the bulk one. Measurement by thermally stimulated depolarization has shown the presence of a residual polarization below 130 K.

Technology of thermally stimulated diagnostics of anisotropy and optical axes in crystals

For implementing the technology of thermally stimulated diagnostics of anisotropy and optical axes in crystals, the sample is thermostated at a temperature not exceeding the melting point, an electric field not exceeding the breakdown field is applied to the sample and polarization is produced for a time greater than the relaxation time at this temperature. After that, without switching off the electric field, the sample is cooled to the liquid nitrogen temperature, following which the field is switched off, the sample is linearly heated to a temperature above the polarization temperature and the resultant thermally stimulated depolarization (TSD) spectra taken along and perpendicular to the optical axis of the crystal are examined. When comparing the spectra the presence of anisotropy is detected and the direction of the optical axes is determined from the magnitude and presence of the TSD maxima.