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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]

The experimental and simulation of dielectric, AC resistivity and dielectric resonance and anti-resonance data on (Na0.5Bi0.5)(NdxTi1-2xNbx)O3] ceramics were carried out using modified Lorentz equations as proposed by us instead of well know and generally applied laws like Arrhenius law and formulas on piezoelectricity to obtain activation energy, relaxation time, piezoelectric charge constant and voltage constant directly from the experimental data. The piezoelectric charge constant (d33) evaluated from the modeling are 864.64 p.m/V and 122.40 p.m/V; whereas the piezoelectric voltage constant (g33) are 10.88 p.m2/C and 8.55 p.m2/C for x = 0.0125 and 0.025 ceramic samples, respectively. [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]

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]

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]

Na0.5-xKxBi0.5-xDyxTiO3ceramics with x = 0.0125, 0.025 and 0.05 were prepared through solid state reaction method. X-ray diffraction studies showed that substitution of K+1and Dy+3ions has not resulted in any change of crystal structure. The SEM graphs indicate the Dy+3doping inhibits the grain growth to some extent. Two abnormal peaks were observed in the temperature dependence of dielectric plots. With the increase of K+1and Dy+3concentrations, the degree of relaxor behaviour and diffusiveness of phase transition is found to increase. Ceramic composition with x = 0.025 exhibits high ferroelectric property with remnant polarization (Pr) around 5.77 μC/cm2and coercive filed (Ec) ∼ 26.22 kV/cm, when compared to other compositions. Lower value of remnant 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. Impedance studies revealed that rare-earth doping restrained the migration of charge carriers. This is attributed to A site vacancy related phenomena. [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]

Effect of doping in Na0:5Bi0:5TiO3 (NBT) with Ce3+ and Sm3+ at the A-site on dielectric behaviour, impedance and conductivity is being reported. Na0:5Bi0:5-xAxTiO3 samples (A being Ce and Sm) are studied with varying values of x. For Na0:5Bi0:5-xCexTiO3 samples x is 0.001, 0.005 and 0.007 and for Na0:5Bi0:5-xSmxTiO3 samples x is 0.05, 0.1 and 0.15. Dielectric constant and loss are studied in the frequency range 10 kHz to 1 MHz and in the temperature range 30-650°C. Impedance and electric modulus studies are undertaken. The relaxations observed in the samples are non-Debye and activation energies for relaxation and conduction are evaluated. [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]

Bismuth in SrBi 4 Ti 4 O 15 is partially replaced with La 3 + to synthesize SrBi (4 - X ) La X Ti 4 O 15 , with x = 0.25,0.5,0.75. The samples have been prepared by sol-gel method using ethylene glycol gel and aqueous solution. This sol-gel process offers some advantages, such as homogeneity and stoichiometry control. The structural characterization of the samples is done using powder X-ray diffraction measurements. The samples are electrically characterized by using dielectric and impedance spectroscopy measurements in the frequency range of 500 Hz to 1 MHz, and temperature range from RT to 600°C. These samples show strong frequency and temperature dependent dielectric relaxations. The power law dependence on a.c conductivity is evaluated. The effect of La 3 + substitution on dielectric, impedance and a.c conductivity is studied. The results obtained are interpreted in terms of the pluckering and on the consequent lattice distortion that is usually present in Bismuth Layer Structured Ferroelectrics. [ABSTRACT FROM AUTHOR]

In a comprehensive study of bismuth compounds, Aurivillius has synthesized a number of mixed bismuth oxides of the formula (Bi 2 O 2 ) 2 + (M x - 1 R x O 3x + 1 ) 2 - . Here M can be mono-, di-, or trivalent ions or a mixture of them, R represent Ti 4 + , Nb 5 + , Ta 5 + etc and x can have values of 2, 3, 4, etc. Bismuth Titanate (Bi 4 Ti 3 O 12 ), is an example of such compounds with x = 3. Modified Bismuth Titanate Ceramics were prepared by using solid state technique with Strontium and Niobium substitution at M and R sites respectively. The dielectric measurements were made from room temperature to 550°C. In the present investigation dielectric maximum is observed at around 350°C. Usually dielectric maximum for Bismuth Titanate occurs at 675°C. The impedance spectroscopy is used to study the relaxation behavior of the sample in view of low T C and low loss. The impedance and electric modulus are studied at different constant temperatures ranging from RT to 550°C,over a frequency range of 100 Hz to 1 MHz. The results obtained in dielectric and impedance studies are presented. [ABSTRACT FROM AUTHOR]

Dielectric data of new [ Ba (Nd x Ti 1 - 2 x Nb x) O 3 ] 0.30 [ Na 0.5 Bi 0.5 TiO 3 ] 0.70 ( x = 0.075 ) relaxor ceramic was modelled using a new modified Lorentz equation (T and ω simultaneously) as proposed by us. The activation energy for thermally activated orientation of dipoles and relaxation times were estimated. Dielectric resonance and anti-resonance data as a function of temperature and angular frequency of other piezoelectric compound [ Ba (Nd 0.1 Ti 0.8 Nb 0.1) O 3 ] 0.35 [ (Na 0.5 Bi 0.5) TiO 3 ] 0.65 was also modelled using the modified Lorentz equation as proposed by us. It is shown that using this equation, it is possible to obtain the polarizability, piezoelectric charge constant, piezoelectric voltage constant and activation energy for resonance and anti-resonance. [ABSTRACT FROM AUTHOR]