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(100-x) BaTiO3(BT)-(x) CoFe2O4(CFO) (X = 10, 20 and 30 wt%) composites were prepared through conventional solid state reaction method by mixing two individual phases by weight. Structure and surface morphology of the composites were observed using X-ray diffraction and Scanning electron microscopy respectively. Polarization study of the BT-CFO composites was done by measuring the polarization (P) against the electric field (E) up to 30 KV/cm, pattern observed showed good ferroelectric behaviour with Pmax= 4.10 µC/cm2for BT-CFO/90-10. In order to estimate the effect of magnetic phase on ferroelectric nature of BT, dielectric and magnetoelectric measurements were also done on the composites and are presented here. [ABSTRACT FROM PUBLISHER]

Ferroelectric ceramic materials NaxK1-xNbO3(NKN), with x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0 are synthesized by solid state double sintering method. The synthesized materials are characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Differential scanning calorimetry (DSC) and Fourier Transform Infrared spectroscopy (FTIR). The x-ray diffraction studies indicate orthorhombic structure except for x = 0.4 (which has monoclinic structure). The SEM micro-graphs indicate a gradual change in the morphology of the samples. Growth of microfibers is observed in x = 0.5 samples. For higher compositions the microfiber morphology is changed.DSC of the samples showed phase transitions. Dielectric constant versus temperature plots indicated ferroelectric to paraelectric phase transitions. The complex impedance plots in higher temperature range are single semi-circles. The equivalent circuits contain parallel combinations of resistance and capacitance elements. [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]

[BaNd0.1Ti0.8Nb0.1O3]0.40[Na0.5Bi0.5TiO3]0.40[CaTiO3]0.20ceramic was prepared through solid state sintering method. The phase and microstructure of ceramic sample were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The XRD results indicate that the ceramic sample have a cubic structure at room temperature. The average grain size was found to be 2 4 μm. The dielectric and piezoelectric properties were also investigated. From capacitance measurements, the values of Kt, Keffand d33at room temperature were 0.816, 0.788 and 15.4 nm.V−1respectively. From modulus data, the Ktand Keffat 325°C are 0.9995 and 0.9994 respectively. The piezoelectric constant (d33) decreased with the increase of temperature and the value of d33at 325 °C was found to be 8.58 nm.V−1. [ABSTRACT FROM AUTHOR]

NBT based ceramic composites (1-x) Na0.5Bi0.5TiO3-xSrTiO3where x = 0.05, 0.10, 0.15 and 0.2 are prepared by solid state sintering route. Individual phases are obtained through sol-gel method. Polarization characterization was done using P-E loop measurements at various temperatures for all samples. Psand d33values obtained are used to estimate electrostrictive coefficient (Q). Curves drawn between strain versus electric field showed butterfly like nature. The electrical characteristics of these composites are investigated using impedance spectra in the temperature range from room temperature (∼30°C) to 500°C at different frequencies in the range of 100Hz-1MHz. The effect of grain and grain boundary interface on the electrical properties of these composites with temperature and composition are evaluated from impedance data analysis. These samples showed a combined relaxation process due to individual phases, resulting in frequency spread. Bulk resistance (Rb) and bulk capacitance (Cb) values are estimated from semicircle fittings. The activation energies for conduction and relaxation for pure and composites helped to assess the conduction mechanism within the samples. The Vogel Fulcher fit helped in estimation of relaxations observed in the samples. [ABSTRACT FROM AUTHOR]

Ceramic compositions [Ba(Nd0.1Ti0.8Nb0.1)O3](1-x)[Na0.5Bi0.5TiO3]xwith x = 0.0, 0.25, 0.40, 0.50, 0.55, 0.60, 0.65 and 0.70 were prepared by modifying the relaxor dielectric material Ba(Nd0.1Ti0.8Nb0.1)O3with ferroelectric Na0.5Bi0.5TiO3using conventional solid state sintering route. The X-ray diffraction studies revealed that the ceramic compositions with x = 0.0, 0.25 and 0.40 are of cubic structure at room temperature and the ceramic compositions with x = 0.60, 0.65 and 0.70 are of rhombohedral structure at room temperature. However, ceramic compositions with x = 0.50, 0.55 show extra peaks indicating that the compositions do not form in to single phase. Dielectric studies revealed that all the ceramic compositions exhibited typical relaxor behaviour and the dielectric maximum temperature is found to increase with the increase of x value. The transition temperatures, degree of relaxor behaviour and diffuseness of phase transitions are related to the steric effect and random distribution of cations at lattice sites respectively. Polarization studies are also done on the samples and results are discussed. [ABSTRACT FROM PUBLISHER]

The (Na0.5-xKxBi0.5-xNdx)TiO3ferroelectric ceramics with x = 0.0125, 0.025 and 0.05 were prepared by solid state reaction route. The dielectric, ferroelectric property and X-ray photoelectron spectroscopy (XPS) studies were investigated on the prepared samples. X-ray studies indicate the formation of single phase perovskite structure with rhombohedral symmetry. Ceramic composition with x = 0.025 exhibit high ferroelectric property with remanent polarization (Pr) around 13.89 μC/cm2 at coercive filed (Ec) ∼ 46.05 kV/cm when compared to other compositions. Lower value of remanent polarization for present ceramic materials when compared to pure sodium bismuth titanate is attributed to domain wall clamping which restrains the macro-micro domain switching. XPS studies indicates that binding energy of Ti 2p and Bi 4f lines are consistent with only one chemical state, Ti+4and Bi+3. On the other hand, in the case of O 1s XPS spectrum, apart from the main peaks attributed to the lattice ions in the perovskite material, extra peaks related to the adsorbed oxygen and oxygen vacancy were also observed. [ABSTRACT FROM PUBLISHER]

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]

Dielectric ceramics with compositions belonging to the Ba(Nd x Ti 1-2 x Nb x )O 3 with varying concentration of x were prepared through Solid State Sintering route using both conventional and microwave sintering. The phase transformations were studied by dielectric measurements in a wide range of temperature and frequency. The relaxor behaviour is almost favoured as the composition deviates more from BaTiO 3 and as the substitution is heterovalent in the 6-coordination number crystallographic site. [ABSTRACT FROM AUTHOR]