Search

SmxBi3–xTiNbO9 (SBTN) with x = 0 , 0.2, 0.4, 0.6, 0.8 and 1.0, a novel type of ceramic was prepared by a conventional solid-state reaction method. X-ray diffraction patterns confirm the formation of a single-phase, and lattice parameters were calculated based on the parent compound Bi3TiNbO9 (BTN). Well-defined grains were seen in the scanning electron microscopy pictures. A kink observed near 400°C for all the samples in the dielectric plot as well as in the stretched exponential parameter (β) vs. temperature plot reveals the dielectric relaxation of the samples. The tolerance factor (t) was found to increase with increase in the size of the A-site (Bi-site) modified ion (Sm). Impedance and modulus spectroscopic studies were conducted to understand the plausible reason for the dielectric relaxation. The relaxation was found to be well-fit with Arrhenius equation. SBTN samples showed lower dielectric loss compared to BTN. The remnant polarization, obtained from experimental, was found to be less than that of theoretically calculated polarization, using Shimakawa's formula. The proposed defect mechanism was interpreted using FTIR and Raman spectroscopic studies. [ABSTRACT FROM AUTHOR]

[Ba(Nd0.1Ti0.8Nb0.1)O3]0.40[Na0.5Bi0.5TiO3]0.50[CaTiO3]0.10 ceramic samples were prepared through solid state sintering route. Impedance and dielectric studies were carried out on the prepared ceramic samples. Impedance and dielectric relaxor behaviour was observed. Grain and grain boundary effects are resolved by equivalent circuit modelling of experimental Cole-Cole data. Electromechanical studies are also carried out on the ceramic samples. Broad resonance and antiresonance peaks have been observed in the modulus data. The values thickness and effective mode of electromechanical coupling factors at 623 K are found to be 0.99983 and 0.99980 respectively. The value of d33 at 673 K and 773 K are found to be 40.32 nm.V-1and 6.44 nm.V-1 respectively. [ABSTRACT FROM AUTHOR]

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]

[BaNd0.1Ti0.8Nb0.1O3]0.40[Na0.5Bi0.5TiO3]0.50[CaTiO3]0.10ceramic was prepared through solid state double sintering method. The XRD results indicate that the ceramic sample have a cubic structure at room temperature. The average grain size was found to be around 4–6 μm. Dielectric studies revealed that the present materials exhibit relaxor behaviour. From piezoelectric studies, it is observed that the resonance and anti-resonance peaks was broad for ceramic sample studied under clamped state when compared to ceramic sample studied under free State. The values of Kt& Keffat room temperature for ceramic samples studied under clamped state were 0.751, 0.718 respectively. Modified Lorentz equation was used to characterize the dielectric and resonance & anti-resonance behaviour and was found to best fit to the experimental data. The activation energy for thermally activated orientation of dipoles was in the range 80–90 μeV. The piezoelectric charge constant (d33) and piezoelectric voltage constant (g33) for the ceramic sample studied under free state are 1.359 × 10−9(m/V) and 2.526 × 10−11(m2/C) respectively. [ABSTRACT FROM PUBLISHER]

[Ba(Nd0.1Ti0.8Nb0.1)O3](1-y)[Na0.5Bi0.5TiO3]yceramics were prepared through solid state sintering (CS) and microwave sintering (MWS) route. The XRD results indicate that the ceramic samples have a cubic structure at room temperature. The dielectric, electromechanical and piezoelectric properties were also investigated. Relaxor behaviour was observed for the present ceramic samples prepared through both the sintering routes. The degree of diffusiveness of phase transition and relaxor behaviour are more for CS ceramic when compared to MWS ceramic with y = 0.40. From modulus measurements, the values of Kt, Keffand d33at 623 K were 0.99983, 0.99980 and 5.273 nm.V−1respectively for MWS ceramic with y = 0.25. The piezoelectric constant (d33) decreased with the increase of temperature. The d33values are higher for the microwave sintered ceramic samples when compared to conventional sintered ceramic samples. [ABSTRACT FROM PUBLISHER]

[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]

Tantalum modified strontium bismuth titanate ceramic discs with general formula SrBi4Ti(4-5x)Ta4xO15 with x = 0, 0.1, 0.2 and 0.3 have been prepared through solid state reaction method. The samples are poled and dielectric constant, loss and AC conductivity measurements are done in the temperature region (30–600°C). Ta5+ doping brought out interesting changes in dielectric phase transition behavior of the samples. Dielectric loss and conductivity measurements indicate the presence of charged defects. The results indicate changes in the distortion of the lattice. The distortion is calculated from the changes in the Curie temperature. AC conductivity results are understood in terms of the unoccupied sites and oxygen vacancies that are present in the samples. [ABSTRACT FROM AUTHOR]

Electrical conduction studies on Ba(Nd0.2Ti0.6Nb0.2)O3 ceramic samples prepared through conventional and microwave sintering route are presented in this paper. D.C. and a.c. conductivities of these samples as a function of temperature from 300--900 K have been studied. Two types of conduction processes are evident from the frequency dependant conductivity plots, i.e. low-frequency conduction due to short-range hopping and high-frequency conduction due to the localized relaxation (reorientational) hopping mechanism. Grain and grain boundary contributions to the conductivity in these samples are obtained from impedance/admittance measurements via equivalent circuit modelling. [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]