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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]

Polycrystalline (Na0.5Bi0.5)(NdxTi1-2xNbx)O3 ceramics with perovskite structure were prepared through the solid state sintering route. The prepared samples were studied for their dielectric, electromechanical and ferroelectric properties. Dielectric measurements showed relaxor behavior. From electromechanical studies, a relatively high electro-mechanical coupling factor, kt (in the range 0.69–0.73) depending upon composition was observed. Among the samples studied, x = 0.0125 exhibited a higher value of remanant polarization (~ 0.50 μC/cm2 at coercive field (Ec = 6.30 kV/cm)). [ABSTRACT FROM AUTHOR]

Polarization and capacitance studies as a function of applied electric field were done on the Nd and Nb-doped polycrystalline ceramic samples. The result indicates that the ceramic samples show low values of remnant polarization. The capacitance value indicates that microwave sintered samples shows higher capacitance tunability when compared to conventional sintered samples. The results obtained from electromechanical studies are also discussed. [ABSTRACT FROM AUTHOR]

The Aurivillius-type compounds with generic formula SrxBi4-xNbxTi3-xO12 (with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized to investigate the effect of Sr and Nb substitution on the bismuth titanate, by a conventional solid state technique. The phase formation of the compound was confirmed through XRD. The dielectric measurements were made at different constant frequencies of 10 kHz, 50 kHz, 100 kHz, 500 kHz and 1 MHz over a wide temperature range. The samples showed a transition from normal ferroelectric behavior to relaxor dielectric behavior with an increasing value of "x". [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]

Dielectric measurements were made over the temperature range 80–300 K at different frequencies (10 kHz, 50 kHz, 100 kHz, 500 kHz and 1 MHz). The degree of relaxor behavior and diffuseness of phase transition were correlated to the cationic disorder at lattice site B. Non-Debye dielectric behavior was observed in the present samples and a modified Arrhenius relation proposed by Chen et al. was found to best describe the frequency dependent dielectric maxima temperature. [ABSTRACT FROM AUTHOR]

Impedance spectroscopic studies on polycrystalline sintered discs of lanthanum doped Na[sub 1/2](La[sub x]Bi[sub 1-x])[sub 1/2]TiO[sub 3] ceramics with x = 0, 0.1, 0.15 and 0.2, have been carried out in the temperature region ranging from room temperature to 550°C and in the frequency range of 100 Hz to 1 MHz. Impedance data is presented in frequency explicit plots and Cole-Cole plots. The relaxation behavior of the charge entities in the above samples is studied as a function of temperature. The structural phase transitions present in the samples showed interesting changes with composition frequency and temperature. An attempt is made to correlate the results obtained to the phase transitions present in the samples. [ABSTRACT FROM AUTHOR]

The Ac conductivity measurements of polycrystalline materials of rare earth substituted Bi[sub 6]Fe[sub 2]Ti[sub 3]O[sub 18] compound at different frequencies (1 kHz-1 MHz) and temperatures (30550°C) are reported. The dc conductivity, ionic hoping rate as well as carrier densities have been extracted from the ac conductivity data. The results show that hoping mechanism dominates at lower temperature. The results are discussed. [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]