Effect of dysprosium substitution on electrical properties of SrBi4Ti4O15

SrBi_4−xDy_xTi₄O₁₅ (with x = 0.02, 0.04, 0.06 and 0.08) powders have been synthesized using the stoichiometric amounts of nitrates and oxides of the constituent materials through sol–gel method. The compound so formed is characterized using X-ray diffraction. The density and lattice parameters are calculated. The impedance and electrical conductivity properties are investigated. The imaginary part of impedance as a function of frequency shows Debye like relaxation. Impedance data presented in the Nyquist plot which is used to identify an equivalent circuit and the fundamental circuit parameters are determined at different temperatures. The results of bulk a.c. conductivity as a function of frequency at different temperatures are presented. The dielectric behavior was investigated. Permittivity was calculated based on the relaxation frequency using an alternative approach based on the variation of the imaginary impedance component as a function of reciprocal angular frequency. The frequency dependence of real and imaginary permittivities was also investigated.     

Impedance spectroscopy analysis of double perovskite Ho<Subscript>2</Subscript>NiTiO<Subscript>6</Subscript>

The electrical properties of double perovskite Ho₂NiTiO₆ (HNT) are investigated by impedance spectroscopy in the temperature range 30–420 °C and frequency range 100 Hz to 1 MHz. The X-ray diffraction analysis reveals that the compound crystallizes in monoclinic phase. The imaginary part of impedance (Z″) as a function of frequency shows Debye type relaxation. The frequency dependence of Z″ peak is found to obey an Arrhenius law with an activation energy of 0.129 eV. Impedance data presented in the Nyquist plot (Z″ vs. Z′) are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HNT exhibits the appearance of both the grain and grain-boundary contribution. The results of bulk ac conductivity as a function of temperature and frequency are presented. The activation energy (0.129 eV), calculated from the slope of log τ versus 10³/T plot, is found to be the nearly same as calculated (0.130 eV) from dc conductivity. The frequency dependent conductivity spectra obey the power law.     

Impedance and a.c. conductivity studies on Ba(Nd0.2Ti0.6Nb0.2)O3 ceramic prepared through conventional and microwave sintering route

Electrical conduction studies on Ba(Nd_0.2Ti_0.6Nb_0.2)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.     

Characterization of electrical behaviour of Si modified BaSnO<Subscript>3</Subscript> electroceramics using impedance analysis

The compounds BaSn_1−x Si _x O₃ (x = 0–15 mol%) have been prepared by high temperature solid-state reaction route. Powder X-ray diffraction pattern of the samples reveal the formation of a single phase solid solution. It was found that single phase compositions have a cubic crystal structure similar to that of pure barium stannate at room temperature. The a.c. impedance analysis has been carried out in the frequency range 100 Hz–1 MHz for temperature ranging from 300 K to 750 K. Analysis of a.c. impedance data using the complex impedance plane gives the a.c. and d.c. resistance of negative temperature resistance of coefficient (NTCR) electroceramics. Complex impedance plane and complex electric modulus formalism are employed to determine the inhomogeneous nature of the electroceramics. This reveals the presence of single elements in the equivalent circuit at elevated temperature. Grain effects are more prominent than that of grain boundary effect at elevated temperature in the material matrix. The electrical conductivity increases sharply with rise in temperature at elevated temperature due to the thermally activated cations. Master modulus analysis provided an evidence of non-exponential type conductivity relaxation occurring in the materials at higher temperatures.     

Impedance and a.c. conductivity studies of Ba(Pr1/2Nb1/2)O3 ceramic

Impedance and electrical conduction studies of Ba(Pr_1/2Nb_1/2)O₃ ceramic prepared through conventional ceramic fabrication technique are presented. The crystal symmetry, space group and unit cell dimensions were estimated using Rietveld analysis. X-ray diffraction analysis indicated the formation of a single-phase cubic structure with space group, ${Pm\overline 3 m}$ . EDAX and SEM studies were carried out to study the quality and purity of compound. To find a correlation between the response of the real system and idealized model circuit composed of discrete electrical components, the model fittings were presented using impedance data. Complex impedance as well as electric modulus analyses suggested dielectric relaxation to be of non-Debye type and negative temperature coefficient of resistance character. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in Ba(Pr_1/2Nb_1/2)O₃. The a.c. conductivity data were used to evaluate density of states at Fermi level, minimum hopping length and apparent activation energy.     

A.c. conductivity studies on the silver molybdo-arsenate glassy system

A new quaternary fast-ion conducting silver molybdo-arsenate [Agl-Ag₂O-(MoO₃ + As₂O₅)] (SMA) glassy system has been prepared using the melt-quenching technique for various dopant salt (Agl) concentrations by fixing the formers (MoO₃ + As₂O₅) composition and the modifier (Ag₂O) to formers (M/F) ratio. The prepared compounds were characterized by X-ray diffraction. The impedance measurements were made on different Agl compositions of the SMA glasses as a function of frequency (6.5 Hz–65 kHz) and temperature (303–343 K), using the Solatron frequency-response analyser (model 1250). The bulk conductivity and the appropriate physical model (equivalent circuit) of the SMA glass were obtained from the impedance analysis. The a.c. conductivity was calculated for different Agl compositions of SMA glasses at various temperatures and the obtained a.c. conductivity results were analysed using Jonscher's Universal Law. The conduction mechanism for the highest conducting SMA glassy compound has been explained using the diffusion path model.     

Conductivity and dielectric studies on (Na0·4Ag0·6)2PbP2O7 compound

Electrical properties of the (Na_0·4Ag_0·6)₂PbP₂O₇ compound were studied using complex impedance spectroscopy in the frequency range 200 Hz–5 MHz and temperature range (484–593 K). Combined impedance and modulus plots were used to analyse the sample behaviour as a function of frequency at different temperatures. Temperature dependence of d.c. and a.c. conductivity indicates that electrical conduction in the material is a thermally activated process. The frequency dependence of the a.c. conduction activation energy was found to obey a mathematical formula.     

Complex impedance studies on tungsten-bronze electroceramic: Pb2Bi3LaTi5O18

Complex impedance analysis of polycrystalline Pb₂Bi₃LaTi₅O₁₈, prepared by a high-temperature solid-state reaction technique has been carried out. XRD analysis indicated the formation of a single-phase orthorhombic structure. Impedance plots were used as a tool to analyse the behaviour of the sample as a function of frequency and temperature. The bulk resistance has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR) type behaviour like that of semiconductors. The ac impedance studies revealed the presence of grain boundary effect at 450°C and showed polydispersive non Debye-type dielectric relaxation. The frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated process. The activation energy for bulk (0.67 eV) and grain boundary (0.73 eV) was estimated from the temperature variation of respective conductivities.     

Dielectric relaxation and ionic conductivity studies of Na<Subscript>2</Subscript>ZnP<Subscript>2</Subscript>O<Subscript>7</Subscript>

The Na₂ZnP₂O₇ compound was obtained by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, infrared analysis and electrical impedance spectroscopy. The impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance R _p and constant phase elements CPE. Dielectric data were analyzed using complex electrical modulus M* for the sample at various temperatures. The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity σ _d.c. follows the Arrhenius relation. The near value of activation energies obtained from the analysis of M″ and conductivity data confirms that the transport is through ion hopping mechanism, dominated by the motion of the Na⁺ ions in the structure of the investigated materials.     

About the peak in the real part of the AC conductivity nearT c in HTSC films

The origin of the peak in the real part of the conductivity of HTSC films nearT _c as a function of temperature and frequency has been analyzed in our experimental setup. It is shown that the peak is the result of a parasitic reactance in the measurement circuit related to the series and parallel equivalent schemes of the measurement circuit. It is demonstrated that the top of the peak is reached when the film resistivity becomes equal to the value of the imaginary part of the circuit impedance. Thus, its location at the temperature scale is determined by the resistance curve. Simultaneously the peak height becomes correspondingly equal to half the inverse value of the imaginary part.     

About the peak in the real part of the AC conductivity nearTc in HTSC films

The origin of the peak in the real part of the conductivity of HTSC films nearT _c as a function of temperature and frequency has been analyzed in our experimental setup. It is shown that the peak is the result of a parasitic reactance in the measurement circuit related to the series and parallel equivalent schemes of the measurement circuit. It is demonstrated that the top of the peak is reached when the film resistivity becomes equal to the value of the imaginary part of the circuit impedance. Thus, its location at the temperature scale is determined by the resistance curve. Simultaneously the peak height becomes correspondingly equal to half the inverse value of the imaginary part.     

Thermal analysis,AC conductivity and dielectric relaxation in Bis(2-methoxyanilinium) hexabromidostannate(IV) dihydrate: (C<Subscript>7</Subscript>H<Subscript>10</Subscript>NO)<Subscript>2</Subscript>SnBr<Subscript>6</Subscript>·2H<Subscript>2</Subscript>O

The (C₇H₁₀NO)₂SnBr₆·2H₂O compound is characterized by using the X-ray powder analysis, thermogravimetric analyses, differential scanning calorimetry (DSC) and complex impedance spectroscopic data. This compound exhibits a phase transition at 300 K which is characterized by differential scanning calorimetry, AC conductivity and dielectric measurements. The measurements of impedance spectroscopic are carried out in the frequency range from 100 Hz to 1 MHz with temperatures varying between 275 and 330 K. The impedance measurements indicate that the electrical properties are strongly temperature dependent. Nyquist plots (?Z′′ versus Z′) show that the conductivity behavior is accurately represented by an Rp//CPE equivalent electrical circuit model. Besides, the frequency dependence of conductivity follows Jonscher’s dynamical law with the relation: \(\sigma (\omega ,T)={\sigma _{DC}}+A(T){\omega ^{S(T)}}\). The relaxation mechanism can be observed in the complex modulus analysis M^* and the complex polarizability α^*.     

Dielectric relaxation studies on [PEO–SiO<Subscript>2</Subscript>]:NH<Subscript>4</Subscript>SCN nanocomposite polymer electrolyte films

Present work deals with findings on dielectric relaxation behaviour and a.c. conduction in a SiO₂-doped polymer nanocomposite electrolyte system, namely, [(100 − x)PEO + xSiO₂]:yNH₄SCN. The formation of nanocomposite has been ascertained by XRD measurements. The effect of salt and filler (SiO₂) on conductivity response of PEO-based nanocomposite polymer electrolyte has been investigated by impedance spectroscopy. The variation of dielectric permittivity, dielectric loss and modulus spectra with frequency and temperature was carried out from impedance spectroscopy data. The a.c. conductivity seems to follow the universal power law.     

Impedance analysis of Pb<Subscript>2</Subscript>Sb<Subscript>3</Subscript>LaTi<Subscript>5</Subscript>O<Subscript>18</Subscript> ceramic

Polycrystalline sample of Pb₂Sb₃LaTi₅O₁₈, a member of tungsten- bronze (TB family, was prepared using a high temperature solid- state reaction technique. XRD analysis indicated the formation of a single-phase orthorhombic structure. The dielectric studies revealed the diffuse phase transition and the transition temperature was found to be at 52° C. Impedance plots were used as tools to analyse the sample behaviour as a function of frequency. Cole-Cole plots showed Debye relaxation. The activation energy was estimated to be 0·634 eV from the temperature variation of d.c. conductivity. The nature of variation of d.c. conductivity with temperature suggested NTCR behaviour.     

Electrical characterization of zirconium substituted barium titanate using complex impedance spectroscopy

This paper reports complex impedance analysis of polycrystalline complex perovskite structured BaZr _0·025Ti _0·975O₃ prepared by solid state reaction method. XRD analysis reveals the formation of single phase perovskite structure. SEM has been used to investigate grain morphology of the material. Impedance plots have been used as a tool to analyse electrical properties of the sample as a function of frequency and temperature. Bulk resistance is observed to decrease with an increase in temperature showing a typical negative temperature coefficient of resistance (NTCR) type behaviour. Nyquist (Cole–Cole) plots show both inter and intra grain boundary effects. Relaxation time is found to decrease with increasing temperature and it obeys the Arrhenius relationship. The variation of d.c. and a.c. conductivity as a function of temperature is also reported.     

AC and DC Conductivity Studies on Lead-Free Ceramics: Sr1–xCaxBi4Ti4O15(x = 0, 0.2, 0.4, 0.6, 0.8)

Sr_1–xCa_xBi₄Ti₄O₁₅ [x = 0, 0.2, 0.4, 0.6, 0.8] ceramics are synthesized by solid-state reactive technique. Structural analyses are done by x-ray diffraction data. Morphological studies were carried out by scanning electron microscope, and the data showed plate-like structures. To understand the conductivity mechanism, frequency and temperature dependency of AC and DC conductivity studies are carried out. The conductivity measurements are done using an impedance analyzer (Wayn–Kerr) in the temperature range 100–600°C. The frequency-dependent AC conductivity at different temperatures indicates that the conduction process follows the universal power law, and the hopping frequency shifts toward higher frequency side with increase in temperature, below which the conductivity is frequency independent. The variation of DC conductivity confirms that the ceramics exhibit negative temperature coefficient of resistance behavior at high temperature. DC conductivity values do not show any linearity with doping concentration; for a particular composition SCBT06, the DC conductivity was low.     

Complex impedance analysis of Sr(NO3)2 and Sr(NO3)2:γ-Al2O3 dispersed solid electrolyte systems

Complex impedance spectroscopic studies were carried out on Sr(NO₃)₂ and Sr(NO₃)₂:-Al₂O₃ dispersed solid electrolyte systems (DSES) in the temperature range 300 to 560° C and the frequency range 100 Hz to 1 MHz. Mole percentage of the dispersoid -Al₂O₃ was varied from 17.2 to 34.2. The d.c. conductivity estimated from the Cole-Cole plots was found to increase with the mole percentage of the dispersoid. Dissipation was found to vary in a manner similar to the variation of conductivity with temperature. A.c. conductivity was found to be frequency dependent in the extrinsic region, but frequency independent in the intrinsic region. The enhanced conductivity in DSES was attributed to the formation of a space-charge layer between the host material and the dispersoid.     

Complex impedance analysis of layered perovskite structure electroceramics—NaDyTiO<Subscript>4</Subscript>

A ceramic oxide (NaDyTiO₄), having layered perovskite structure, has been prepared by a standard high-temperature solid-state reaction technique. X-ray diffraction (XRD) studies have confirmed material formation under reported condition along with the presence of impurity (Na₂Dy₂Ti₃O₁₀) as the minor phase. Complex impedance spectroscopy (CIS) analysis has been carried out to investigate its microstructure and electrical properties as a function of frequency and temperature. CIS analysis has indicated that the electrical behavior of the material sample shows negative temperature coefficient of resistance (NTCR) typical to a semiconductor. Impedance studies have also indicated the presence of temperature dependent relaxation process in the material with a spread of relaxation time. The d.c. conductivity of the material as evaluated from the impedance spectrum has been observed to be ∼10⁻⁹ Scm⁻¹ at room temperature (RT). It has been observed to increase as a function of temperature with a maximum of ∼10⁻⁵ Scm⁻¹ at 550∘C. The conductivity variation shows a cross over from Mott-type hopping phenomena at lower temperatures to a thermally activated Arrhenius type behavior at high temperature.     

Effect of ZrO2 on conductivity of PVC-PMMA-LiBF4-DBP polymer electrolytes

The preparation and characterization of composite polymer electrolytes of PVC-PMMA-LiBF₄-DBP for different concentrations of ZrO₂ have been investigated. FTIR studies indicate complex formation between the polymers, salt and plasticizer. The electrical conductivity values measured by a.c. impedance spectroscopy is found to depend upon the ZrO₂ concentration. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and results discussed.     

Electrical properties of ITO/benzylated cyclodextrins (β-CDs (Bz))/Al diode structures

Abstract

Investigations of the electrical characteristics of benzylated cyclodextrins (β-CDs (Bz)) diodes are reported. We present current–voltage characteristics and impedance spectroscopy measurements performed on partially benzylated cyclodextrins β-CDs (Bz) thin films in sandwich structures ITO/b-CDs (Bz)/Al. The static electrical characterizations show a space charge limited conduction (SCLC) and a conductivity with power low frequency behavior characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor R_p and capacitor C_p network in series with resistor R_s. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution. We estimated from the capacitance voltage characteristic an acceptor concentration of about 10¹¹ cm^?3 due to trap states.