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Novel polycrystalline materials of bismuth substituted barium titanate, namely, BaBixTi1-xO3-δ, (x = 0.025, 0.075, 0.125 and 0.175) was prepared by sol-gel chemical route and characterized by X-ray diffraction and scanning electron microscopy. Bismuth ion was added in place of titanium of B-site of ABO3 perovskite structure and both the site-balance as well as charge-balance was considered. The substitution of bismuth for Ti-site is clearly seen in both the XRD as well as IR spectroscopic data. Dielectric and impedance analysis were also made on the present novel ceramics. The above mentioned substitution involves ionic compensation, through creation of cation vacancies and is explained by proposing the defect dynamics. The results were corroborated with dielectric and complex impedance analysis for further understanding of ionic motion in this kind of disordered diffused materials. [ABSTRACT FROM AUTHOR]

Impedance measurements were made on technological important ferroelectric ceramics, namely PZT and La0.75 Bi3.25Ti3O12 (BLT), in the frequency range of 100 Hz to 1 MHz, from room temperature to 500°C. Combined impedance and modulus spectroscopic analysis along with the detailed conductivity (ac and dc) data was used to understand the heterogeneity of the ceramics and the results were corroborated with temperature coefficient of dc-conductivity (figure of merit) data for the further understanding. AC-conductivity plots against frequency at different temperatures for PZT and BLT suggest the response of obeying Jonscher's and modified Jonscher's law, respectively. [ABSTRACT FROM AUTHOR]

Impedance spectroscopic measurements were carried out on lead based ferroelectric ceramics, namely PZT, PLZT and PMN-PT, in the frequency range of 0.1 Hz-1 MHz. Spectroscopic plots showed broad peaks, and are found to shift towards higher frequency side. Apart from this, both Z'' and M'' spectroscopic peaks are found to coincide almost in the same frequency region. This indicates approximated-Debye behavior. Frequency dependent conductivity plots show two slopes at lower and higher frequency regions. Low frequency relaxations are found to be non-exponential. Bulk relaxation vs. temperature plots are found to obey Arhenius linear fit. The relaxation at lower frequency and higher are attributed to Kohlrausch-Williams-Watt (KWW) type and migration of slow oxygen and lead vacancies. The results are corroborated to the conduction barrier hopping mechanism and new Eyraud's conductivity model. [ABSTRACT FROM AUTHOR]

A and B site modified new bismuth layered structure ferroelectric ceramics of the Aurivillius family were prepared by the solid-state route. Impedance measurements were performed on these samples to understand the relaxation effects in the frequency range of 100 Hz to 1 MHz. From the detailed impedance and modulus spectroscopic analysis, it is found that the aliovalent modified B-site enhances the relaxor-like nature, compared to A-site substitution. These results were corroborated with ac-conductivity transport analysis. In this connection, a defect formula is also proposed. The results are discussed. [ABSTRACT FROM AUTHOR]

AC-impedance spectroscopic studies are carried out on lead magnesium niobate (PMN) and La-modified PMN-PT (lead magnesium niobate-lead titanate), Pb 1 - x La x [(Mg 1 + x / 3 Nb 2 - x / 3 ) 0.65 Ti 0.35( 1 - x / 4 ) ]O 3 , ceramic, with x = 0 to 0.07. Complex modulus and impedance plots exhibit two depressed semicircles and one depressed semicircle, respectively for PMN. This is attributed to the nearly same capacitance of grain and grain boundaries and higher grain boundary resistance than the grain resistance for PMN. Un-doped MPB composition of PMN-PT (0/65/35) and La-doped PMN-PT composition (7/65/35) also show similar complex modulus and impedance plots of PMN but in these samples the grain boundary capacitance was found to be higher than the grain capacitance. Cole-Cole plot shows two depressed semicircles, exhibiting grain and grain-boundary contributions in all the samples. La substitution is found to result in a broad peak in the frequency dependence of the imaginary part of the impedance and the modulus, for the temperature range 300–600°C. The maxima in the impedance and the modulus are found to shift towards higher frequencies with increasing temperature for all La-doped PMN-PT compositions, indicating a deviation from Debye behaviour. La-substitution results in broadening of the ε( T ) peak, and a marked frequency dependence of ε max (T max ), similar to that observed in PMN. It is believed that La-substitution induces the relaxor-like permittivity characteristics in MPB composition of PMN-PT by constructing higher-resistive and lower-capacitive grains, and grain boundaries. [ABSTRACT FROM AUTHOR]

GdBi[sub 5]Fe[sub 2]Ti[sub 3]O[sub 18] (GBFT), a compound of Aurivillius family, was prepared by solid state reaction method. Complex impedance measurement was made on these samples from room temperature to 500°C in the frequency range of 1 kHz-1 MHz. Cole-Cole plots were found to become very broad near 400°C. Dielectric and dc conductivity measurements were made on these samples. The results are analysed to understand the conductivity mechanism. [ABSTRACT FROM AUTHOR]