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In this paper, detailed studies of effect of small amount of manganese substitution (at the zirconium site) on the structural, micro-structural, and electrical characteristics of lead zirconate titanate of Pb(Zr0.35–xMnxTi0.65)O3;x = 0, 0.02, 0.06, 0.10 (PZMT)) have been reported. The materials were prepared by using standard ceramic technology. The formation of the compounds and their basic crystal data have been studied through X-ray diffraction (XRD) method. The crystallite size and lattice strain of the compounds, evaluated from Scherrer's and Hall Williamson (H-W) equations, is found to be in the range of 40–50 nm and 11 × 10−4 to 50 × 10−4, respectively. Microstructures of different magnifications, revealing the surface nature of the compounds, have been recorded by field emission scanning electron microscope (FESEM). Effect of Mn+4 ions on electrical behavior (electrical impedance (Z*), electrical modulus (M*), conduction and relaxation phenomenon) of PZMT systems, over wide range of temperature and frequency, has been studied. [ABSTRACT FROM AUTHOR]

In this paper, a novel antenna based on LTCC for UHF RFID tag is proposed. The antenna is constituted by the metal lines on surfaces of the first two layers of LTCC substrate. The uppermost layer with meander lines can effectively reduce the area, and the lower one adopts mesh structure to ensure both shielding effect and the quality of products. Testing results show that, at the operating frequency of 915 MHz, S11 parameter and VSWR of the antenna are 14.71dB and 1.39, respectively. In addition, the antenna has advantages of omni-direction radiation pattern and easy impedance matching. [ABSTRACT FROM AUTHOR]

In this article, the synthesis (through a mixed oxide route, calcination temperature = 850 °C, sintering temperature = 870 °C, for time= 6 h) and characterization (structure, dielectric, and electrical properties) of Gd modified bismuth titanate Bi4Ti3O12 of a chemical composition Bi3.8Gd0.2Ti3O12 of Aurivillius family in ceramic form have been reported. The development of an orthorhombic structure (with a minor secondary phase) with a space group B2ab has been confirmed by analyzing room temperature X-rays diffraction pattern/data. Studies of some electrical parameters like loss tangent, dielectric constant, electric impedance, and conductivity have provided valuable data and information on conduction mechanism, structure-properties relationship, etc., in the 25–500° C temperature range at different frequencies (1 kHz − 1MHz). The presence of grain, grain boundary is confirmed from the Nyquist plot. The Nyquist plot also confirms the existence of non-Debye relaxation in the material. The frequency and temperature significantly impact the material's various properties (dielectric and electrical). [ABSTRACT FROM AUTHOR]

In this paper an experimental study of different piezoelectric materials for energy harvesting applications, as well as experimental results for various types of piezoelectric materials and piezoelements were presented. Various types of hot-pressed and conventionally sintered PZT piezoceramics, porous PZT piezoceramics, and multilayer PZT/PZT ceramic piezocomposites with diverse ferroelectric “hardness” were fabricated, optimized and tested. Experimental results comprising cyclic loading at different load resistances and mechanical stresses for different types of piezoelements were presented. It was shown that porous ceramics (relative porosity 20%, d33= 410 pC/N, ϵT33/ϵ0= 1100) provide 1.5–2 times higher power efficiency at cyclic loadings than the dense hot-pressed ceramics and can be used as piezogenerators at low loading pressures (up to 5 MPa). The possible applications of developed materials in energy harvesting devices as well as the empirical criteria of piezoelectric materials efficiency were discussed. [ABSTRACT FROM PUBLISHER]

Aurivillius phase (Li,Ce) doped CaBi4Ti4O15(CBT) ceramics were prepared using the conventional solid state methods. The crystal structure and microstructure were determined by X-ray diffraction and scanning electron microscopy. It was found that the (Li,Ce) ions diffused into the A site of CBT's pseudo-perovskite structure and formed a single Aurivillius type structure. The Curie-temperature (TC) of CBT based ceramics decreased whereas the piezoelectric coefficient (d33) was improved with an increase of (Li,Ce) dopants. The detailed electrical properties for Ca0.85(LiCe)0.075Bi4Ti4O15ceramics in the high temperature region were determined using electrochemical impedance spectra. It was found that oxygen vacancies make a major contribution to both electrical conduction and dielectric relaxation. The ac conductivity was found to obey Jonscher's universal law. In addition, the physical nature of electrical conduction and dielectric relaxation was addressed in this paper. [ABSTRACT FROM AUTHOR]

Energy recovery from wasted or unused power has been the topic of discussion for a long time. In recent years, industrial and academic research units have focused on harvesting energy from mechanical vibrations using piezoelectric transducers. These efforts have provided the initial research guidelines and have brought in light the problems and limitations of implementing the piezoelectric transducer. There are three major phases/steps associated with piezoelectric energy harvesting: (i) mechanical-mechanical energy transfer, including mechanical stability of the piezoelectric transducer under large stresses, and mechanical impedance matching, (ii) mechanical-electrical energy transduction, relating with the electromechanical coupling factor in the composite transducer structure, and (iii) electrical-electrical energy transfer, including electrical impedance matching, such as a DC/DC converter to accumulate the energy into a rechargeable battery. This paper deals with detailed energy flow analysis in piezoelectric energy harvesting systems with typical stiff 'Cymbals' and flexible piezoelectric transducers, in order to provide comprehensive strategies on how to improve the efficiency of the harvesting system. Energy transfer rates are practically evaluated in the above all steps. [ABSTRACT FROM AUTHOR]

Complex impedance and electric modulus spectroscopies were used to investigate the dielectric relaxation and conductivity of random oriented BiFeO3 thin films. Thermally activated charge transport models yielded activation energies of eV, which is consistent with an electrical conduction dominated by oxygen vacancies. The non-Debye behavior of impedance and electric modulus relaxations were modeled by Cole-Cole functions. Results suggest a coexistence of components from both long-range and localized relaxation in the studied BiFeO3 films dominated by grain boundaries. The dielectric relaxation induced by electric field does not follow the Arrhenius formalism. [ABSTRACT FROM AUTHOR]

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]

Electric properties of lithium heptagermanate Li2Ge7O15single crystal have been studied in AC external field (101–105Hz) in the temperature range 300–700 K. It has been shown that below 500 K conductivityσis determined by polarization processes whereas above this temperature charge transfer phenomena become dominant. It is assumed that at high temperatures conduction is determined by mobile interstitial lithium ions АLi. The spectra of complex impedanceρ*testify for hopping АLiconduction and accumulation of charge carriers near to blocking Pt electrodes. [ABSTRACT FROM PUBLISHER]

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 radial vibration of piezoceramic disc stack is investigated by theoretical analysis, numerical simulation, and experimental measurement. Using the piezoelectric constitutive equations, the radial resonant frequency is derived by solving the admittance of the stack and setting it approaching infinity. The frequency equation is calculated numerically with software. Calculation results are compared with the frequency measured by Impedance Analyzer and Laser Scanning Vibrometer. Theoretical calculation shows agreement with experimental measurement. The error is less than 1.5%. Measured results also indicate that the resonant frequency of the disc stack is almost same with a disk at the radial vibration mode. [ABSTRACT FROM AUTHOR]

The temperature dependences of the dielectric properties and conductivity of the La1 - xSrxMnO3 single crystals (x = 0.1, 0.11, 0.125) are investigated in a wide temperature range. It is found that the giant dielectric permittivity arises due to the pre-percolation regime of the charge separation. These single crystals display also the colossal magnetocapacitance effect. The features of the temperature dependence of these dielectric properties are explained by the nanoscale dynamic inhomogeneties appearing due to the charge and spin ordering. [ABSTRACT FROM AUTHOR]

The density of hollow particle (microballoon) filled composites called syntactic foams can be varied by two methods. The first method is the variation in microballoon volume fraction and the second method is the variation in the microballoon wall thickness, while keeping their volume fraction the same. A comparison of compressive properties of syntactic foams having microballoons of four different wall thicknesses in five volume fraction each is presented here. It is found that the compressive strength and modulus vary linearly with respect to the foam density. Dielectric constant, dielectric loss and electrical impedance are measured for four syntactic foam compositions with respect to temperature and frequency. Dielectric constant and loss are found to decrease with increase in frequency and with decrease in temperature in the range of 40–140°C. [ABSTRACT FROM AUTHOR]

Impedance spectroscopy has been used to characterize grain and grain-boundary resistivities of Ni-doped SrTiO 3 ceramics. The role of grain boundary was changed with Ni-doping concentration. The phenomenon was also interpreted by accounting for microstructural differences. The corresponding relaxation times were also used to confirm the interpretation of complex impedance spectra. Overlapping of Grain boundary and electrode relaxation processes can be separated above about 400°C. Admittance spectra may be suitable to extract grain boundary impedances at relatively low temperatures. The values of grain and grain-boundary activation energy obtained by this method were relatively close to those reported earlier. [ABSTRACT FROM AUTHOR]

Resistive type humidity sensor is fabricated using nanometer lanthanum ferrite. The impedance property of the sensor is measured in relative humidity (RH) range 11% to 98%, and in frequency range 10 Hz to 100 kHz. The complex impedance plots (Cole-Cole plots) are drawn. A circuit with resistors and capacitors is used as an equivalent circuit of the conduction process of the sensor. With the changing of the resistance and capacitance in the circuit, the shape of the complex impedance curve changes gradually from one semicircle to two semicircles, and finally only the second semicircle remains. This coincides with what happens in the Cole-Cole plots of our experiment. The mechanism of the humidity sensor is analyzed in terms of the complex impedance plots and the equivalent circuit. In low RH range, the conduction process is dominated by the decomposition and polarization of the grains of the sensing material, and in high RH range, by the decomposition and polarization of the adsorbed water. [ABSTRACT FROM AUTHOR]

Room temperature radial mode piezoelectric response of Lanthanum modified Lead Zirconate Titanate (Pb(Zr0.57Ti0.43)O3+X at%La) (PLZT) is characterized by Vector Impedance Spectroscopy. Piezoelectric parameters (electromechanical constants KP, K31, elastic compliance sE11, strain constants d31, dh, voltage constant g31and planar piezoelectric constants radial mode coupling constant kp, piezoelectric constant ep31and mechanical constant cp11) have been determined for La doping ranging from 3 to 12 at%. Piezoelectric parameters KP, kp, d33and d31peak at 5–6 at%of La while dielectric constantsεT33,εP33and piezoelectric constant ep31peak at 8 at%. An average value of Poisson's ratioσEis found to be 0.34±0.01. The conductivity of PLZTs follows the universal behavior. [ABSTRACT FROM AUTHOR]