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Ba1-xRexTiO3 ceramics (Re = Nd&Pr with x = 0.002 & 0.004) were prepared through microwave sintering route using 5% SiO2 as sintering aid. The dielectric, impedance and DC resistivity studies were carried out over a wide range of temperature. From dielectric studies, it is observed that the transition temperature increased with the substitution of rare earth ions. The room temperature dielectric constant for the Nd (x = 0.002) doped barium titanate is higher when compared to other compositions and the value is 13,600.28. Impedance studies revealed relaxation behaviour. In the present study grain, grain boundary and sample-electrode effects were separated out by using Cole-Cole data. From the DC resistivity studies, it is observed that Pr (x = 0.004) doped barium titanate ceramic showed one order of magnitude PTCR effect. [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]

Lead free piezoelectric ceramic Ba1-xRexTiO3(Re = Ce and Pr withx= 0.003) were prepared through microwave sintering route using 5% SiO2as sintering aid. The dielectric, impedance and piezoelectric properties were studied over a wide range of temperature. Pr doped barium titanate showed higher value of dielectric constant around 15,099. The electromechanical coupling factors at 225°C are 0.9985 and 0.9978 for Ce and Pr doped barium titanate ceramics respectively. The d33values for Ce and Pr doped barium titanate ceramics at 225°C are 368 nm.V−1and 470 nm.V−1respectively. The d33value decreased with the increase of temperature and the values at 600°C are 10 nm.V−1and 8 nm.V−1for Ce and Pr doped barium titanate ceramics respectively. [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]

A new equation is proposed to describe the simultaneous temperature and frequency dependence of dielectric constant and impedance of relaxor ferroelectric compounds. It is applied to Ba(NdxTi1-2xNbx)O3relaxor compounds by non linear curve fitting to experimental data to check its validity in terms of fitted parameters obtained which have logical values. The validity can also be known from the regression value. This new equation may be used to characterize the dielectric behaviour of other relaxor ferroelectric compounds. [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]

BaBixTi(1−x)O3−δceramics are prepared by sol-gel reaction method with different x values (x = 0, 0.05 and 0.1). Structural property of all compositions is studied by XRD and compared with the standard patterns (ICSD card 27977). The crystalline size increases with increase the Bi concentration. The temperature dependence of impedance of BaBixTi1−xO3 (x = 0, 0.05, 0.1) compositions is studied in the frequency range of 100 Hz-1M Hz. Relaxation times (τ) are studied for the different BaBiO3concentrations doped into barium titanate ceramics. The impedance characteristics of the laminated type graded composite materials of BaTiO3+ Ba0.95Bi0.05TiO3+BaTiO3and BaTiO3+ Ba0.90Bi0.1TiO3+BaTiO3are also studied. The impedance data is analyzed using established models and equivalent circuit parameters are evaluated. The equivalent circuits obtained consist of series or parallel combination of a resistance and a constant phase elements. The results are interpreted in terms of materials properties. [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]

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]

The effect of lanthanum doping on the electromechanical properties of lanthanum-doped sodium bismuth titanate was studied. The ferroelectric system under investigation was Na1/2(LaxBi1-x)1/2TiO3 ceramics, with x=0, 0.1, 0.15 and 0.2. Admittance measurements were carried out in the frequency range of 100 Hz to 13 MHz and in the temperature range from room temperature to 550°C. Combined impedance and admittance spectroscopy was used to analyze admittance data. The electromechanical parameters were calculated from the resonant and anti-resonant frequencies obtained from vector admittance plots. The electromechanical coefficients for pure sodium bismuth titanate ceramic samples were found to be much larger than the reported values. Also, it was observed that lanthanum-doping decreased the values of electromechanical coupling coefficients. [ABSTRACT FROM AUTHOR]