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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]

Ba(NdxTi1-2xNbx)O3 (with x = 0.025, 0.05, 0.1, and 0.2) and Na0.5Bi0.5(NdyTi(1-2y)Nby)O3 (y = 0.0125, 0.025, and 0.05) ceramics were prepared through solid state sintering route. In the present study modulus resonance studies at high temperatures were carried out on the above ceramics. Higher piezoelectric performance in terms of parameters like thickness mode of electromechanical coupling factor and piezoelectric charge constant were observed for the ceramic compositions operating at higher temperature regime (798–873 K). In the case of ceramic composition with y = 0.0125, 0.025, and 0.05, the piezoelectric charge constant operating at 798K are 26.16 nm.V−1, 17.74 nm.V−1, and 24.33 nm.V−1, respectively. [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]

Polycrystalline ceramics SrBi4-xSmxTi3.9Pr0.1O15(where x = 0, 0.1, 0.2 and 0.3) were prepared by sol-gel pechini method. The phase formation was confirmed using X-ray diffraction technique and was found to be orthorhombic. Complex impedance spectroscopy (CIS) technique revealed the presence of both grain and grain-boundary effects in the materials. Grain resistance and grain boundary resistance decreases with increasing temperature confirming the NTCR behaviour of the samples. The relaxation times obtained from impedance studies were used to interpret complex impedance nature of the samples. The temperature dependent conductivity obeys the Arrhenius relationship. The impedance studies indicate the non-Debye type of the frequency dispersion for all the samples. [ABSTRACT FROM AUTHOR]

Novel polycrystalline materials of bismuth substituted barium titanate, namely, BaBixTi1-xO3-δ, (x = 0.025, 0.075, 0.125 and 0.175) was prepared by sol-gel chemical route and characterized by X-ray diffraction and scanning electron microscopy. Bismuth ion was added in place of titanium of B-site of ABO3 perovskite structure and both the site-balance as well as charge-balance was considered. The substitution of bismuth for Ti-site is clearly seen in both the XRD as well as IR spectroscopic data. Dielectric and impedance analysis were also made on the present novel ceramics. The above mentioned substitution involves ionic compensation, through creation of cation vacancies and is explained by proposing the defect dynamics. The results were corroborated with dielectric and complex impedance analysis for further understanding of ionic motion in this kind of disordered diffused materials. [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]

Impedance spectroscopic measurements were carried out on lead based ferroelectric ceramics, namely PZT, PLZT and PMN-PT, in the frequency range of 0.1 Hz-1 MHz. Spectroscopic plots showed broad peaks, and are found to shift towards higher frequency side. Apart from this, both Z'' and M'' spectroscopic peaks are found to coincide almost in the same frequency region. This indicates approximated-Debye behavior. Frequency dependent conductivity plots show two slopes at lower and higher frequency regions. Low frequency relaxations are found to be non-exponential. Bulk relaxation vs. temperature plots are found to obey Arhenius linear fit. The relaxation at lower frequency and higher are attributed to Kohlrausch-Williams-Watt (KWW) type and migration of slow oxygen and lead vacancies. The results are corroborated to the conduction barrier hopping mechanism and new Eyraud's conductivity model. [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]

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]

The effect of lanthanum doping is studied on electromechanical properties of lanthanum doped sodium bismuth titanate. The ferroelectric system under investigation is Na 1/2 (La x Bi 1-x ) 1/2 TiO 3 ceramics, with x = 0, 0.1, 0.15 and 0.2. Dielectric and impedance studies 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. The relaxation behaviour 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. Admittance measurements were carried out in the frequency range of 100 Hz to 13 MHz and in the temperature range of 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. And also, it is observed that the lanthanum doping decreased the values of electromechanical coupling coefficients. [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]

Dielectric, conductivity and piezoelectric properties have been studied on (Ba0.997Nd0.003)TiO3 ceramic samples prepared through microwave sintered (MWS) and conventional sintered (CS) routes and the results are presented in this paper. The room temperature dielectric constant at 10 kHz for CS and MWS samples are 1245 and 5250 respectively. Room temperature dielectric constant in MWS sample was almost four times higher than that of the CS sample. The value of Kt is found to be 0.998 and 0.997; whereas the value of d33 is 7.72nmV-1 (573 K) and 444.66nmV-1 (573 K) for CS and MWS samples, respectively. In the present study almost 57 times enhancement in piezoelectric charge constant (d33) is observed for the MWS Ba0.997Nd0.003TiO3 ceramic when compared to the CS ceramic. [ABSTRACT FROM AUTHOR]