The dielectric permittivity (ɛ′), electric modulus (M″), and ac conductivity (σac) of pure polyvinylidene fluoride (PVDF) and PVDF containing 3 wt.% RCl3 (R = Er or Gd) were measured. The incorporation of 3 wt.% of ErCl3 or GdCl3 within the PVDF matrix is found significantly to increase its ɛ′ and σac. All investigated samples show different relaxation processes within the studied temperature and frequency ranges. The first process is αa-relaxation, which occurs around the glass transition temperature, Tg. The second process is αc-relaxation, which is associated with the molecular motions in the crystalline region of the main polymer chain. Third is the ρ-relaxation which observed for pure PVDF at low temperatures and high frequencies. The frequency dependence of σac shows that the conduction mechanism for pure PVDF and PVDF containing 3 wt.% of RCl3 is correlated barrier hopping (CBH). The binding energy of the carriers was calculated based on the CBH model. Finally, the results obtained in this work are discussed and compared with those for 3 wt.% LaCl3-doped PVDF and similar materials.

Silica nanoparticles were synthesized by a sol-gel method and mixed with different amounts of polyvinyl chloride (PVC) to get nanocomposite films. The samples were characterized by XRD, HR-TEM, SEM, and FTIR. High resolution transmission electron microscopy (HR-TEM) proved that the average particle size of the nanosilica is 15 nm. The scanning electron microscopy (SEM) showed that the nanosilica was well dispersed on the surface of the PVC films. Fourier Transform Infrared (FTIR) spectra for nanocomposite films intimate a significant change in the intensity of the characteristic peaks of the functional group with addition of nanosilica. The optical band gap was found to decrease with the addition of nanosilica while the refractive index increased. The dielectric constantε′, the dielectric loss modulusM′′, and AC conductivity(σAC)were also studied. It was found thatε′increases with temperature for all samples, clear dielectricα-relaxation observed from dielectric lossM′′around the glass temperature (Tg), and this could be related to micro-Brownian motion of the main PVC chain. The activation energy was calculated, and the AC conductivity could be a hopping one. The results of this work are discussed and compared with previously obtained data.

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We present measurements of the magnetic torque, specific heat and thermal expansion of the bulk transition metal dichalcogenide (TMD) superconductor NbS2 in high magnetic fields, with its layer structure aligned strictly parallel to the field using a piezo rotary positioner. The upper critical field of superconducting TMDs in the 2D form is known to be dramatically enhanced by a special form of Ising spin orbit coupling. This Ising superconductivity is very robust to the Pauli paramagnetic effect and can therefore exist beyond the Pauli limit for superconductivity. We find that superconductivity beyond the Pauli limit still exists in bulk single crystals of NbS2 for a precisely parallel field alignment. However, the comparison of our upper critical field transition line with numerical simulations rather points to the development of a Fulde-Ferrell-Larkin-Ovchinnikov state above the Pauli limit as a cause. This is also consistent with the observation of a magnetic field driven phase transition in the thermodynamic quantities within the superconducting state near the Pauli limit.