Structural, dielectric and impedance characteristics of CoTiO3

Abstract

The present work reports the synthesis and characterization of the ilmenite-type rhombohedral structured CoTiO3 ceramic. The polycrystalline powder of CoTiO3 was prepared by the mixed-oxide technique. X-ray structural analysis of the compound confirmed the formation of a single-phase compound. The study of microstructure by scanning electron microscopy shows that the compound has well defined grains which are distributed uniformly throughout the surface. It shows that the grain size lies in the range of 8–10 μm. The Fourier transform infrared spectroscopy (FTIR) studies confirm the presence of TiO, TiOTi, TiOO, CoO bond in the studied compound. The frequency dependence of dielectric constant was explained on the basis of Maxwell–Wagner mechanism and Koop's phenomenological theory. The frequency-temperature dependence of impedance analysis shows that the bulk effect dominates up to 250 °C, and the appearance of second semicircular arc above 280 °C indicates the presence of grain boundary effect in the sample. The depressed semicircles in Nyquist plot with depression angles clearly indicate the distribution of relaxation times in the ceramic samples. It also shows that the material has negative temperature co-efficient of resistance similar to that of semiconductors. Similar behavior has also been observed in the study of IV characteristics of the material. Through the study of dc conductivity of CoTiO3 and using the relation; ln σdc α Ea/KBT, activation energy of the compound was calculated. The frequency dependence of ac conductivity is explained on the basis of Correlated barrier Hopping Model.