Transport and magnetic properties of PANI-HCl organic conductor

Novak, Mario (2010) Transport and magnetic properties of PANI-HCl organic conductor. Doctoral thesis, Faculty of Science > Department of Physics.

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Abstract

We investigated the influence of the doping level (Y = [Cl]/[N]) on the electrical transport and static magnetic properties of the conducting polymer polyaniline (PANI). PANI was synthesized by an oxidative polymerization, and doped with hydrochloric acid (HCl). The investigated samples differ by the level of doping (from the fully doped (Y = 0.5) to the undoped one (Y = 0)), and were produced by pressing the PANI-HCl powder into pellets. The transport measurements show that the electrical conductivity follows the relation ln σ (T) α −(T0/T)α , for all samples. The exponent changes its value depending on Y and temperature (T). More precisely, α = 1/2 for the samples with Y < 0.3, and 2/5 for the samples with Y > 0.3, at low T. At high T the exponent α changes to 1/4 for the samples with Y < 0.4, and to ∼ 1 for all other samples. One of the samples (the most conductive one) also shows a transition α = 2/5 → 1/4 → 1, with increasing of T. All obtained values of α and the temperature induced transitions between them can be well described by the Fogler, Teber and Shklovskii variable-range-hopping model (FTS-VRH). According to the FTS-VRH model the low-T conductivity is governed by the Coulomb interaction which opens a ”soft” Coulomb gap at the Fermi energy, therefore, α = 2/5 and 1/2. At the high T the influence of the Coulomb gap is weakened due to the increase in temperature, and α goes to 1/4 and 1. Exponent α = 1 indicates transition from the VRH to the nearest- neighbour hopping. Static magnetic measurements give that the magnetic susceptibility Χ (T) can be described as the sum of the Curie-like and the Pauli-like susceptibility. Furthermore, a correspondence between σ (T) and Χ (T) was found. Namely, the parameters of (T) and Χ(T) change values around the same temperatures, which indicates the connection between the charge and spin carriers. The samples were also subjected to the elemental analysis and the X-ray diffraction.

Item Type: Thesis (Doctoral thesis)
Keywords: polyaniline ; synthesis ; electrical conductivity ; magnetic susceptibility
Supervisor: Kokanović, Ivan
Date: 14 July 2010
Number of Pages: 146
Subjects: NATURAL SCIENCES > Physics
Divisions: Faculty of Science > Department of Physics
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 22 Dec 2013 22:21
Last Modified: 22 Dec 2013 22:21
URI: http://digre.pmf.unizg.hr/id/eprint/58

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