The influences of calcination temperature and doping with cobalt in A–site on structural and dielectric properties of CaCu3-xCoxTi4O12 (CCCxTO, x = 0.00, 0.02 and 0.10) ceramics sintered at 1050 0C for 8h were investigated. The ceramic samples are prepared by the conventional solid-state method using high purity oxide powders, and they are calcined at 850 °C, 950 °C and 1050 0C for 4h. The X-ray diffraction (XRD) analysis of pure and doped CCTO samples calcined at 950 °C and 1050 0C showed no traces of any other secondary phases, while impurity phases alongside CCTO phase in the x=0.00 sample calcined at 850 0C was observed. Scanning electron microscopy (SEM) investigation showed an increase in grain size with increasing of Co content and calcining temperature. Dielectric measurements indicated that the dielectric constant of the pure CCTO calcined at 1050 0C/4h has a low value in the frequency range of 1kHz up to 1MHz, whereas the substitution of Co up to x = 0.10 into CCTO caused a huge increase in the dielectric constant value of the calcined samples which is equal to 153419 and 18957 at 950 °C and 1050 0C respectively. The complex impedance analysis of all samples shows a decrease in resistance with an increasing temperature, which suggests a semiconductor nature of the samples

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The effect of Barium doping is studied on ferroelectric properties of (1-x)(Na 0.5 Bi 0. 5)TiO 3-xBaTiO 3 with(x = 0.00; 0.0 3; 0.05; 0.06; 0.07; 0.08 and 0.10) prepared through solid state sintering route. X-ray diffraction along with Rietveld refinement revealed a gradual change in crystal structure from rhombohedral to tetragonal with increasing BaTiO3 doping in the compound. SEM images have shown a uniform distribution of grains and change in grain size with BaTiO 3 concentration. Dielectric and dispersive studies have been carried out. The rhombohedral distortion of the unit cell slightly increased and ferroelectric transition temperature, T m decreased with the increase of Barium content and all compositions of (1-x)(Na 0.5 Bi 0. 5)TiO 3-xBaTiO 3 ceramic materials reveal diffuse phase transition that is marked by a strong frequency dispersion of the permittivity which would be related with the cation disorder in the A site of the unit cell. Combined impedance and electrical propriety were used to analyze impedance data. The electromechanical parameters were calculated from the resonant and anti-resonant frequencies from the evolution of the permittivity according to the frequency plots. The electromechanical coefficients for (1-x)(Na 0.5 Bi 0. 5)TiO 3-xBaTiO 3 with all compositions were found to be much larger than that of pure Na 0.5 Bi 0.5 TiO 3.

In this paper, the structural properties of (1-x)(Na0.5Bi0.5)TiO3-xBaTiO3 ceramic system for (x = 0.00, 0.03, 0.05, 0.06, 0.07, 0.08 and 0.1) were studied. Moreover, the samples are obtained through the conventional solid-state method. The effect of calcination temperature ranging from 800 to 1000 ºC was investigated, using X-ray diffraction data and Rietveld refinement method, which permit to verify the morphotropic phase boundary at x = 0.05-0.07. The Raman spectral data were examined by inspecting the changes in their respective peak positions, full width at half maximum (FWHM) and intensities by increasing BaTiO3 composition. It was found that morphotropic phase boundary in the studied system resides at composition of x = 0.05. The analysis of both Rietveld refinement and Raman spectroscopy of the samples showed a distortion of Na0.5Bi0.5TiO3 lattice when Ba 2+ ions were added, as well as the ceramic structures underwent a gradual distortion by increasing the composition fraction of BaTiO3.