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Polycrystalline LaFe0.9Ni0.1O3 is prepared by the solid state reactions route. X-ray diffraction is used to analyse the phase purity of the compound. Impedance spectra of LaFe0.9Ni0.1O3 over the frequency range of 1 Hz to 10 MHz are investigated at different temperatures from 100 to 373 K. Two relaxation processes with different relaxation times are observed at each temperature. An equivalent circuit model (R1Q1) (R2Q2) is applied to explore the physical parameters associated with grains and grain boundaries. Frequency and temperature dependence of the relaxation processes and extracted parameters are discussed in terms of hopping between Fe+4 and Fe+3 and trap state scattering at grain boundaries. A change in conduction mechanism from variable range hopping to adiabatic small polaron hopping at 296 K is evident from these results. Traps are active below 296 K in capturing the charge.

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Polyaniline (PANI)/Ag nanocomposites were prepared by separate synthesis of silver nanoparticles by inert gas condensation, incorporating in the 1-methyl-2-pyrrolidinone (NMP) solution of polyaniline emeraldine base (PANIEB) and then cast into films at 120 °C. X-ray diffraction confirmed the presence of ∼67 nm silver nanoparticles in the polyaniline matrix. From the thermogravimetric analysis it is observed that the nanocomposite films have a higher degradation temperature than the pure PANI film. Scanning electron microscopy showed a uniform distribution, with spherical and granular morphology for low concentration of Ag nanoparticles, whereas for higher concentration (1.0% Ag) nanorods are formed. The impedance spectroscopic studies of NMP plasticized nanocomposite films suggest microphase separation into reduced and oxidized repeat units. Incorporation of silver nanoparticles in PANI reduces the charge trapping centres and increases the conducting channels, which causes a tenfold decrease in the real part of impedance.

Gold nanoparticles are synthesized by the reduction of gold salt using extract of tea leaves in 1-methyl-2pyrrolidinone (NMP) solution. Transmission electron microscopy (TEM) confirmed the formation of gold nanoparticles having average size of ∼20 nm. These nanoparticles have been incorporated in NMP solution of polyaniline emeraldine base (PANIEB) to cast the nanocomposite films. Thermogravimetric analysis (TGA) revealed that the thermal stability of the nanocomposites has improved as compared to the pure PANI. TEM confirmed the presence of gold nanoparticles in polyaniline matrix. The impedance spectroscopic studies showed that gold nanoparticles have considerable effects on the electrical properties of PANI by reducing the charge trapping centers and increasing conducting channels, which causes substantial decrease in the real part of impedance.