Evolution of grain boundary conduction with increasing temperature in pure and Ti doped Co ferrite materials

We report on the structural, temperature, and frequency dependent impedance studies of Ti doped cobalt ferrite material (CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf>) in comparison with the pure CoFe<inf>2</inf>O<inf>4</inf>. XRD and Raman spectroscopy studies confirm the inverse spinel crystallization of the materials with space group of Fd-3 m. Scanning electron microscope images shows the microcrystalline nature of the particles. Homogeneity, stoichiometry, and ionic states of the ions in the composition were confirmed by energy dispersive X-ray analysis and X-ray photoelectron spectroscopic studies. Temperature and frequency dependent real (Z′) and imaginary (Z″) part of the impedance shows the existence of relaxation processes and their distribution in CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials. Complex impedance spectroscopy studies at low temperatures shows that the conductivity in these materials is predominantly due to the intrinsic bulk grains. With increasing the temperature, evolution of grain boundary conduction is clearly seen through the appearance of a second semi-circle in the complex impedance plots. Room temperature total dc conductivity of both CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials is found to be 5.78 × 10^-8 and 1.61 × 10^-7 S/cm, respectively. Temperature variation of dc electrical conductivity follows the Arrhenius relationship and the activation energies for CoFe<inf>2</inf>O<inf>4</inf> corresponding to grain (0.55 eV for CoFe<inf>2</inf>O<inf>4</inf>), grain boundary (0.52 eV), and total conduction (0.54 eV) are discussed. Observation of well distinguishable grain and grain boundary conductions and the low conductivity values in CoFe<inf>2</inf>O<inf>4</inf> and CoFe<inf>1.95</inf>Ti<inf>0.05</inf>O<inf>4</inf> materials indicates that these materials are promising candidates for the high frequency applications.