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Samarium modified SrBi4-xSmxTi4O15 (x = 0, 0.13, 0.43 and 0.78) ferroelectric ceramics of Aurivillius family were prepared by conventional solid state reaction method. X-ray diffraction studies confirm the formation of a single-phase. Microstructural images show randomly oriented palate-like structure. Broad dielectric peaks were found to obey the modified Curie-Weiss law. The overall inherent ferroelectric nature was explained on the basis of the Avrami model. Furthermore, with increasing the Sm3+ content, the grain morphology and diffusive parameters have shown a comprehending impact on the ferroelectric (hysteresis) behavior. [ABSTRACT FROM AUTHOR]

Bismuth layered structure ferroelectric materials of Aurivillius family have been attracted on account of their inherent-ferroelectric properties. Rare earth modified two layered compound, namely, Bi3TiNbO9has been found to be a relaxor ferroelectric material, and therefore much attention is being concentrated to enhance the dielectric properties with different modifications. In view of this, Sm-modified novel ceramic(Bi2SmTiNbO9) was prepared by the conventional solid-state reaction method. Impedance spectroscopic measurements were made as a function of frequency at different temperatures. Electrical studies were also made, and the results were corroborated to the Raman spectroscopic data. [ABSTRACT FROM AUTHOR]

Bismuth titanate (BT-‘Bi4Ti3O12’) is one of the extensively studied materials of the Bismuth layered structure ferroelectric (BLSF) family for its large spontaneous polarization along c-axis. In the present investigation, we have synthesised SmxBi4-xTi3O12(x = 0.37, 0.57, 0.72) ceramics using the conventional solid-state reaction method. The dielectric anomaly was observed near 450°C. Well-broad hysteresis loops were observed above room temperature up to 100°C. The coercive field (Ec) and consistent remanent polarization (Pr) values with temperature, compared to BT, indicates that the title compound has good promising ferroelectric-nature. This phenomenon is attributed to the easy recovery of defects (such as oxygen vacancies) accumulated at grain-interfaces, above room temperature, resulting in to well-hysteresis behaviour. The results were further confirmed with remanent polarization (2 Pr vs. temperature) plots. [ABSTRACT FROM AUTHOR]

Single-phase bismuth layered structure ferroelectromagnet (BLSFEM) LaGdxB5-xFe2Ti3O18of composition (x = 0.1, 0.2, 0.4, 0.6 and 0.8), novel ceramics were prepared by solid state route. Electrical and impedance measurements were made on the ceramics. Complex Impedance spectroscopic plots showed the signature of magnetic ion (Gd) and the results were corroborated to the Debye and Gaussian fitting curves. The variation of dielectric and modulus with temperature plots were used to explain dielectric phenomenon. An attempt is made to understand the effect of magnetic (Gd) ion on A site of (Bi2O2)2+(LaGdxBi3-xTi3Fe2O16)2−, layered perovskite (title) compound. [ABSTRACT FROM AUTHOR]

The bismuth layer structured ferroelectric (BLSF) ceramics consisting of four-layers (BaLa0.75Bi3.25Ti4O15) and five-layers (Ba2La0.75Bi3.25Ti5O18) were prepared by the conventional solid-state reaction method. Summerfield ac-conductivity scaling analysis was used to evaluate the electrical behavior and the ac-conductivity isotherm curves. The relaxation results were corroborated with the Raman Peak positions and full width at half maximum was obtained by using Lorentzian peak fit method. Finally, the results were compared with the two-layered relaxor-compound (Bi2.45La0.55TiNbO9) and technologically standard three-layered compounds (La0.75Bi3.25Ti3O12; BLT). The dielectric relaxation of Bi2.45La0.55TiNbO9was verified using modified Curie-Weiss law and Vögel-Fulcher relationship. An attempt is made to realize the typical collective nature of the ionic conductivity of the samples. [ABSTRACT FROM AUTHOR]

Oxygen-deficient and charge- imbalanced polycrystalline materials of three-layered Auruvillius compound, namely Sr2Bi2Nb3O12(SBN), was synthesized by Sol-Gel method. X-ray diffraction analysis was made on SBN and lattice parameters were calculated. Electrical impedance and Pyroelectric measurements were performed on SBN. The broad peak observed in the dielectric permitivity data indicates that the transition is diffused phase transition (DPT) and the modified Curie-Weiss law was used to describe the DPT of SBN. The sharp intensity peak observed at 176 and 219 cm−1in Raman spectra is an indicative of Sr-O-Sr and Sr-O-Bi bonds and its competitive interactions. The peaks of FTIR spectra appeared at 610 cm−1confirmed the same. The nature of difffused type was attributed to compositional heterogenity and the results were corroborated with the log-log spectroscopic plots of impedance,modulus and permitivity for better understanding of the disorder ferroelectric behavior of the sample. The broad semicircle behavior observed in the complex impedance aswell as modulus plot, associated with grain and grain boundary, confirm the same. [ABSTRACT FROM AUTHOR]

Lanthanum and vanadium modified polycrystalline material of La0.75Bi3.25Ti2.9625V0.03O12(BLVT) of Aurivillius family, was prepared by conventional solid-state reaction method. X-ray diffraction showed single phase with orthorhombic structure. Electron microcopy was done on as-sintered and oxygen-annealed samples. Impedance studies of BLVT showed multiple impedance relaxations. Based on the impedance factor (related to full width at half maximum) and master plots, the relaxations are found to be collectively competitive. A broad dielectric peak and Curie-Weiss diffused parameter indicates diffused phase transition. Complex impedance analysis along with the log-log spectroscopic plots was studied on BLVT at 500°C. But complex impedance plot of BLVT showed single broad semicircle, unlike La0.75Bi3.25Ti3O12(BLT), which showed three semicircles on separately coated silver- and platinum- ceramic disks. However, complex modulus plot (complimentary to impedance) of BLVT showed three semicircles, which clearly indicates the tendency of formation of space charges, which might result in the accumulation of defects at electrode-ferroelectric interfaces, and considered to be a characteristic feature of the sample. In view of this, some of the BLVT samples were annealed in oxygen- and vacuum. Detailed ac-conductivity analysis suggests that double oxygen vacancies play vital role in conduction phenomenon. [ABSTRACT FROM AUTHOR]

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]

Tri (Dy3 +) and pentavalent (Nb+5) modified new polycrystalline material of Aurivillius family (Dy0.75Bi3.25Ti2.9625Nb0.03O12) was prepared by solid-state reaction method and the lattice parameters were calculated by using X-ray diffractogram. Impedance measurements were carried out from room temperature to 500°C in the frequency range of 100 Hz to 1 M Hz. Impedance spectroscopic plots show non-Debye type and detailed ac-conductivity analysis was also employed to understand the heterogeneity of the present electro-ceramics. The results were corroborated with the proposed defect formula and in addition, thermal stimulated current measurements show that the present sample has an excellent pyroelectric response. [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]

Polycrystalline hexagonal Yttrium Manganites (YMnO3) were prepared by solid-state route. X-ray studies revealed the formation of homogenous and single phase material in hexagonal structure. Dielectric, impedance, electrical, magnetic and magnetoelectric measurements were performed on the YMnO3 ceramics. Dielectric and impedance studies show relaxations near 200°C. Complex spectroscopic analysis, in the temperature range of 30–300°C from 1 kHz to 1 MHz, showed non-Debye relaxations. Ac and dc electrical measurements were extracted to understand the transport mechanism: Ac conductivity data is found to obey ‘Universal’ power law with exponent 0.8. Low temperature magnetization measurements were performed to understand the magnetic nature of the sample. Room temperature magnetoelectric (ME) measurements were also performed and corroborated with the magnetization data. [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]

Glasses of various compositions in the system (100 - x )Li 2 B 4 O 7 - x (SrO-Bi 2 O 3 -Nb 2 O 5 ) (10 ≤ x ≤ 60) (in molar ratio) were prepared via a conventional melt-quenching technique. The glassy nature of the as-quenched samples was established by Differential Thermal Analyses (DTA). X-ray powder diffraction (XRD) and Transmission Electron Microscopic (TEM) studies confirmed the amorphous nature of the as quenched and crystallinity in the heat-treated samples. The formation of nanocrystalline layered perovskite SrBi 2 Nb 2 O 9 (SBN) phase, in the samples heat-treated at temperatures higher than 550°C, through an intermediate fluorite phase in the LBO glass matrix was confirmed by both the XRD and High Resolution Transmission Electron Microscopy (HRTEM). The samples that were heat-treated at two different temperatures, 550 and 625°C, (containing 0.35 and 0.47 μm sized SBN crystallites) exhibited broad dielectric anomalies in the vicinity of ferroelectric to paraelectric transition temperature of the parent SBN ceramics. A downward shift in the phase transition temperature was observed with decreasing crystallite size of SBN. The observation of pyroelectric and ferroelectric properties for the present samples confirmed their polar nature. [ABSTRACT FROM AUTHOR]