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[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]

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]

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]

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]

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]

Nano particulate Barium Bismuth Titanate (BaBixTi1-xO3-δ) materials with (x = 0.25, 0.075. 0.125 and 0.175) were prepared through sol-gel chemical route (Pichini method) and the XRD patterns were indexed on the basis of tetragonal-BaTiO3 phase. The electrical impedance measurements were carried out on the samples by using Auto Lab PGSTAT30 impedance analyzer in the frequency region 100 Hz-1 MHz from RT to 500°C. Impedance spectroscopic and complex explicit plots show the presence of both bulk and grain boundary effects, and impedance spectroscopy is shown to be an efficient method capable of detecting the conductivity species and estimating the electrical conductivity as well as activation energy value. Finally, the results are interpreted in terms of the defect dynamics and conduction mechanisms taking place in the samples. [ABSTRACT FROM AUTHOR]

Tri (Dy3 +) and pentavalent (Nb+5) modified new polycrystalline material of Aurivillius family (Dy0.75Bi3.25Ti2.9625Nb0.03O12) was prepared by solid-state reaction method and the lattice parameters were calculated by using X-ray diffractogram. Impedance measurements were carried out from room temperature to 500°C in the frequency range of 100 Hz to 1 M Hz. Impedance spectroscopic plots show non-Debye type and detailed ac-conductivity analysis was also employed to understand the heterogeneity of the present electro-ceramics. The results were corroborated with the proposed defect formula and in addition, thermal stimulated current measurements show that the present sample has an excellent pyroelectric response. [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]

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]

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]

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]

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]