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.

Nonlinear Quantum Phenomena During the Polarization of Nanometer Layers of Proton Semiconductors and Dielectrics

This paper investigates the influence of the structure and parameters of the degenerate quasi-discrete energy spectrum of relaxers (protons) on the mechanism of nonlinear quantum diffusion polarization in nanoscale layers of hydrogen bonded crystals (HBC) in a wide range of parameters of fields (100 kV/m - 1000 MV/m) and temperatures (0-1550 K). The temperature dependence of the quantum transparency of the parabolic potential barrier for protons in HBC is calculated using the Gibbs quantum canonical distribution for the ensemble of non-interacting protons (ideal proton gas balanced with the ions of anion sub-lattice) moving in an onedimensional potential field of a crystalline lattice (in the field of hydrogen bonds) with a zone structure distributed by energy levels. The influence of "zero" oscillations of protons on the temperature dependences of the proton subsystem kinetic coefficients in HBC is considered. It is revealed that proton tunneling influences the nonlinear space-charge polarization kinetics in HBC at high (150-550 K) and ultrahigh (550-1550 K) temperatures when crystalline layer thickness ranges from 1 to 10 nm. The results of theoretical studies (based on earlier experiments) are bound to be prospective for the prediction of HBC-class (KDP, DKDP) ferroelectrics properties, studying the second-order nonlinear optical effects of femtosecond lasers, and the development of memory cells for non-volatile high-speed memory devices.

Effect of Gd3+ Substitution on Thermoelectric Power Factor of Paramagnetic Co2+-Doped Calcium Molybdato-Tungstates

A series of Co2+-doped and Gd3+-co-doped calcium molybdato-tungstates, i.e., Ca1−3x−yCoy▯xGd2x(MoO4)1−3x(WO4)3x (CCGMWO), where 0 < x ≤ 0.2, y = 0.02 and ▯ represents vacancy, were successfully synthesized by high-temperature solid-state reaction method. XRD studies and diffuse reflectance UV–vis spectral analysis confirmed the formation of single, tetragonal scheelite-type phases with space group I41/a and a direct optical band gap above 3.5 eV. Magnetic and electrical measurements showed insulating behavior with n-type residual electrical conductivity, an almost perfect paramagnetic state with weak short-range ferromagnetic interactions, as well as an increase of spin contribution to the magnetic moment and an increase in the power factor with increasing gadolinium ions in the sample. Broadband dielectric spectroscopy measurements and dielectric analysis in the frequency representation showed a relatively high value of dielectric permittivity at low frequencies, characteristic of a space charge polarization and small values of both permittivity and loss tangent at higher frequencies.

Discussion on Structural, Optical, Thermal, Mechanical, Dielectric and Third-Order NLO Properties of 3-Nitroanilinium Chloride Single Crystals for Optoelectronic Applications

Preferable, third-order nonlinear optical (NLO) single crystal, 3-Nitroanilinium chloride (3NACL) was auspiciously synthesised by slow evaporation technique. The crystal system of synthesised 3NACL crystal is triclinic with centrosymmetric space group was identified by single crystal XRD studies. All the functional groups present in the sample and its respective vibrations are analysed through FTIR analysis. UV-Vis transmittance spectrum revealed that the synthesised material was 83% transmittance and it cut-off wavelength was 276nm. The mechanical stability and thermal property of grown 3NACL crystals were ascertained by Vickers micro hardness analysis and TG/DTA analysis. The intermolecular interaction of the 3NACL was scrutinized by Hirshfeld surface analysis. Dielectric studies revealed that dielectric constant and dielectric loss were high at lower frequency region due to the space charge polarization. Inclusion free 3NACL crystal was used to analyse the Laser damage threshold (LDT) studies and its calculated LDT value was 4.3 GW/cm2. The third-order NLO parameters (β = 7.5472x10− 12 m/W, η2 = 5.6931x10− 19 m2/W, χ3 = 2.9491x10− 13 esu) of the 3NACL material was statutory evaluated by Z-scan studied. Here, β and η2 are positive value due to the saturated absorption and self-focusing effect was observed in open and closed aperture z-scan curve. Above all these findings 3NACL was suitable material for NLO and optoelectronic applications.

Effect of Temperature on the Dielectric and Magnetic Properties of NiFe2O4@MgFe2O4 and ZnFe2O4@MgFe2O4 Core-Shell

The core-shell NiFe2O4@MgFe2O4 (NiF@MgF) and ZnFe2O4@MgFe2O4 (ZnF@MgF) are stable nanocomposites. The experimental results showed perfect dielectric and magnetic properties different than their components. The experimental data revealed that the mutual effect between the core and the shell increases the space charge polarization. Also, the samples showed semiconducting-metallic behavior, which varies according to the temperatures and the frequencies. Furthermore, the magnetization M(T) was studied using the Faraday balance method of all samples. The obtained results of M(T) exhibit good magnetic properties of the core-shell samples, particularly the sample ZnF@MgF, where it possesses magnetization higher than the pure ferrite phase (MgFe2O4) and Curie temperature (TCm) higher than the room temperature, and this is new for Zn-ferrite. Besides, the effective magnetic moment (µEff) and the Curie-Weiss constant (θ) were obtained from the magnetic susceptibility χ(T) protocols.

Effect of Temperature on the Dielectric and Magnetic Properties of NiFe2O4@MgFe2O4 and ZnFe2O4@MgFe2O4 Core-shell

The core-shell of nanoferrites showed quite different properties rather than the nanoferrites counterpart. The nanocomposites of NiFe2O4@MgFe2O4 (NiF@MgF) and ZnFe2O4@MgFe2O4 (ZnF@MgF) are chemically stable and showed very good dielectric and magnetic properties. In this investigation, the temperature-dependent dielectric constant, dielectric loss, and ac-electrical conductivity were measured up to 650 K under different alternating electric field frequencies from 100 Hz to 8 MHz. The obtained data revealed that the mutual effect between the core and the shell samples increases the space charge polarization. Also, the samples showed the semiconducting-metallic behavior which varies between SP, CBH, and QMT models according to the temperatures and the frequencies. Furthermore, the magnetization M(T) was studied of all samples using the Faraday balance method in the temperature range 300-500K. The experimental results of M(T) exhibit good magnetic properties of the core-shell samples, particularly the sample ZnF@MgF. The novelty in this work is an unexpected behavior of ZnF@MgF which possesses magnetization higher than the pure ferrite phase (MgFe2O4), and Curie temperature (TCm) higher than the room temperature. So, the sample ZnF@MgF is a ferrimagnetic substance. Besides, the effective magnetic moment (mEff) and the Curie-Weiss constant (q) for all samples were obtained from the magnetic susceptibility c(T) protocols.

The Impact of Space Charge Polarization on Light-soaking Phenomena in Non-Fullerene Organic Solar Cells

Revealing the microscopic origin of the unstable nature in organic solar cells (OSCs) is a key issue for further device optimization. Here, we identify that the light-soaking process seen in...

Effects of Heat-Treatment on the Microstructure, Electromagnetic Wave Absorbing Properties, and Mechanical Properties of SiCN Fibers

SiCN fibers can not only be used for reinforcement of composites materials but also for electromagnetic wave (EMW) absorbing applications in a high-temperature oxidizing environment above 1,200°C. In this work, the microstructural evolution and EMW absorbing properties of SiCN fibers after annealing at 1,300–1,600°C in N2 atmosphere were investigated. Results showed that the amorphous SiCN fibers presented poor EMW absorbing properties when the annealing temperature was below 1,400°C. As the annealing temperature increased to 1,500°C, the EMW absorbing properties could been largely enhanced with a minimum reflation loss value of -55.8 dB and an effective absorption bandwidth value of 2.5 GHz. The enhanced EMW absorbing properties should contribute to the formation and growth of grain boundaries and defects among the amorphous fiber matrix and turbostratic graphite carbon, which could enhance the space charge polarization at the heterogeneous interfaces and increase the conductivity of the SiCN fibers. Meanwhile, SiCN fibers retained a rather high tensile strength of ∼1.0 GPa after annealing at 1,500°C, which showed it to be a promising candidate for reinforcing the stealth ceramic matrix composites used in harsh environments.