Structural, dielectric and impedance properties of Ca(Fe2/3W1/3)O3 nanoceramics

The polycrystalline nanoceramics (similar to 60 nm) of Ca(Fe2/3W1/3)O-3 (CFW) were synthesized by mechanochernical and solid-state reaction techniques. Preliminary X-ray structural analysis of CFW suggested the formation of single-phase compound in tetragonal crystal system (distorted structure of ideal perovskite). The large distortion (similar to 16%) is supported by a large deviation of tolerance factor t = 0.86 from unity (for ideal perovskite). The SEM micrograph shows the polycrystalline nature of the sample with different grain sizes, which are inhomogeneously distributed through the sample surface. Detailed studies of dielectric and impedance properties of the material in a wide range of frequency (1 kHz-1 MHz) and temperatures (300-630 K) show that these properties are strongly temperature and frequency dependent. The nature of variation of AC conductivity exhibits a progressive increase in AC conductivity on increasing temperature. The oxygen vacancies, space charge and mobile charge carriers play an important role in relaxation and conduction process. The relaxation process in the material was found to be of non-Debye type. (c) 2007 Elsevier B.V. All rights reserved.