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In our earlier studies we have shown procedure for the estimation of activation energy and relaxation times directly from the dielectric and AC conductivity data simultaneously dependant on T and ω using modified Lorentz equation instead of well-known Arrhenius, modified Arrhenius and Vogel-Fulcher laws. In the present paper we have carried out similar experimental and simulation studies on the dielectric and AC conductivity data using modified Lorentz equations on the ceramic compound (Ba0.997Pr0.003TiO3). The obtained results on the activation energy and relaxation times are presented in this paper. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

Modified Lorentz and Gauss equation is proposed to describe the temperature dependence of dielectric constant for bismuth layered structure ferroelectric materials i.e. Sr1-2xNaxNdxBi4Ti4O15. The validity of the proposed equation was checked from the regression value obtained. The activation energy for orientation of dipoles, static dielectric constant and infinite dielectric constant obtained from the non linear curve fitting to experimental data by using modified Lorentz and Gauss equation have reasonable values. Modified Lorentz equation is found to be the best fit to the experimental dielectric data. The above modified equations may also be used to describe the dielectric behaviour of other normal ferroelectric materials which show sharp transitions. [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 (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]

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]

Sodium Potassium Niobate ceramic with perovskite structure has been prepared through solid state reaction using conventional double sintering method. The starting materials are mixed in the stoichiometric proportion. The compound is characterized through x-ray diffraction to ensure the formation of single phase. From this data, the lattice parameters are determined. The temperature dependence of the dielectric constant and loss factor are obtained over a wide frequency range. Both dielectric constant and loss factor show two peaks. The dielectric and loss peaks observed at lower temperature are found to be of less intensity. The second dielectric anomaly observed around 430°C is found to follow Curie-Weiss law. The curie constant ‘C’ is observed to be around 10 5 °C. Impedance measurements are also made in the temperature range 30°C to 550°C in frequency range 500 Hz to 1 MHz. Dispersion of impedance with frequency show peaks, which vary both with temperature and frequency. The relaxation times are obtained from these peak frequencies. Activation energy of relaxation is calculated and the results are presented. [ABSTRACT FROM AUTHOR]