Tailored conductivity behavior in nanocrystalline nickel ferrite

In this letter, we report an important issue in nanoparticle synthesis by the "bottom up" approach. By controlling the pH of the starting mixture of the salts we have been successful in obtaining the desired conductivity of nanosized nickel ferrite. X-ray diffraction and transmission electron microscopy confirmed the size, structure, and morphology of the nanoferrites. All the materials are typical semiconducting oxides whose conductivity depends on the pH of the starting salt solution. Direct current and alternating current conductivity studies coupled with thermoelectric measurements and the resultant activation energies help us to propose the mechanism of conductivity in these ferrites. X-ray photoelectron spectroscopy studies are indicative of Ni3+ presence in p-type ferrite. The n- and p-type conductivity in these materials is attributed to the hopping due to the presence of Fe3+ and Ni3+ ions, respectively. (C) 2004 American Institute of Physics.