Abstract
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.
Highlights
Polyvinylidene fluoride (PVDF) has widely been investigated because of its many good properties such as chemical resistance, high dielectric permittivity, semicrystalline structure, and unique pyroelectric and piezoelectric behaviors.[1,2,3] There are two phases of PVDF, namely, the α–phase and the β-phase
The frequency dependence of σ ac shows that the conduction mechanism for pure PVDF and PVDF containing 3 wt.% of RCl3 is correlated barrier hopping (CBH)
Since the temperature dependence of ε for pure PVDF and RCl3-doped PVDF samples is similar to the temperature dependence of the electric modulus (M ), we have shown ε (T) for the two doped samples at 100 kHz only (see the inset of Fig. 8(b))
Summary
Polyvinylidene fluoride (PVDF) has widely been investigated because of its many good properties such as chemical resistance, high dielectric permittivity, semicrystalline structure, and unique pyroelectric and piezoelectric behaviors.[1,2,3] There are two phases of PVDF, namely, the α–phase and the β-phase. Rare earth (R3+) ions have specific chemical characteristics, including a relatively large size, low capacity for covalent-bond formation, and electrostatic interactions with negatively charged ligands. Because of these features and the electronic structure, such lanthanides can form complexes with bonds that are mainly ionic (electrostatic) in nature.[6,7] Polymers and polymeric composites have steadily gained importance in our life. Numerous investigations have been conducted on different polymer-metal composites in order to understand their physical properties.[8,9] The addition of fillers into a polymer matrix may modify its properties by causing interphase interactions or the formation of an interface at the boundary between the polymer matrix and filler particles.[10,11] stabilization or improvement of the mechanical, electrical, and thermal properties of dielectrics can be achieved.[12, 13].
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