Ferrites with the general formula Li 0.5 Ni 0.75−x/2 Cd x/2 Fe 2 O 4 (where x = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by the standard double sintering ceramic method. X-ray diffraction analysis confirmed the single phase spinel structure of the samples. The variation of saturation magnetization (M s ) was studied as a function of Cd content. The dielectric constant (ε ) and dielectric loss tangent (tan δ) were measured at room temperature as a function of frequency in the range 100 Hz-1 MHz. These parameters decrease with increasing frequency for all of the samples. The compositional variation of ε and ρ DC show an inverse trend of variation with each other.

Composites with compositions (x)Ni 0.8 Cu 0.2 Fe 2 O 4 + (1 − x) Ba 0.9 Pb 0.1 Ti 0.9 Zr 0.1 O 3 , in which x varies as 0, 0.15, 0.30, 0.45 and 1 mol%, were prepared by a standard ceramic technique. X-ray diffraction was used to carry out the structural analysis. The microstructural analysis was carried out by scanning electron microscopy. The variation in dc resistivity with temperature was studied in the temperature range 300-773 K. The variation of dc resistivity with temperature shows a semiconducting behavior. From ac conductivity measurements in the frequency range 100 Hz to 1 MHz it is concluded that the conduction in the present composites is due to a small polaron hopping. The variations in dielectric constant and loss tangent were also studied. The magnetoelectric effect (ME) (dE/dH) H was measured as a function of intensity of the dc magnetic field. The maximum value of ME conversion factor was observed to be 431 μV cm −1 Oe −1 for the 15%Ni 0.8 Cu 0.2 Fe 2 O 4 + 85%Ba 0.9 Pb 0.1 Ti 0.9 Zr 0.1 O 3 composite. The ME coefficient has been explained in terms of ferrite-ferroelectric content.

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Polyaniline/cobalt oxide composites were synthesized by an in situ chemical polymerization method with ammonium persulfate as an oxidizing agent. This was a single-step polymerization process for the direct synthesis of the emeraldine salt phase of the polymer. The polymers were characterized with X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectral analysis. The formation of mixed phases of the polymer together with the conducting emeraldine salt phase was confirmed by spectroscopic techniques. Hightemperature conductivity measurements showed thermally activated behavior. A change in the resistance was observed with respect to the relative humidity when the pellets were exposed to a wide humidity range of 10-95%.