Complex Impedance Analysis Research Articles

Preparation and physicochemical properties of pure and O2- doped nanocomposites based on cadmium and manganese sulfides

Pure and O2- (2.5/5.0 wt%) doped (CdS)1−x(MnS2)x nanocomposites (with x = 0.0/0.25/0.50/0.75/1.0) have been (for the first time) prepared by a simple solvothermal method (with pulsed microwave heating) and characterized structurally, chemically and physically (thermally, electrically, optically and magnetically) by adopting the available techniques. The prepared samples (except the pure and doped CdS) are found to be multi-phased nanocomposites, and are paramagnetic in nature. Average crystallite sizes obtained are within 5.6 and 13.9 nm, and the thermal stability has been found to increase in proportion with the amount of CdS present. Bandgap energies obtained are within 1.8 and 2.2 eV, and significant photoluminescence peaks have been observed; DC and AC electrical measurements along with complex impedance analysis have provided useful results. The present study indicates that the prepared nanocomposites (based on CdS and MnS2) are expected to find utility in optoelectronic and energy devices.

Analyses of negative real permittivity behavior, AC conductivity and impedance properties of (YxEu1-x)Ba2Cu3O6.5 ceramics

In the present study, the dielectric, ac conductivity, and complex impedance properties of (YxEu1-x) Ba2Cu3O6.5 perovskite ceramics where x: 0; 0,4; 0,6; 1 have been examined from room temperature to 523 K between 1 Hz and 20 MHz frequency range. The ceramics have been synthesized by solid-state reaction method. The XRD analyses of the samples pointed out that they crystallize in an orthorhombic structure. While the highest orthorombicity factor has been observed for YBa2Cu3O6.5 ceramic, the reduced orthorhombicity in the other ceramics has been associated with the Eu substitution. On the other hand, the dielectric analyses of the samples have revealed a negative real permittivity (NRP) property of all ceramics regardless of the Eu substitution ratio and temperature. The origin of the NRP phenomenon has been explained based on the Drude model. However, it has been reported that the frequency interval at which the NRP is valid is maximum for x≥0.6 at high temperatures (T > 500 K). Additionally, both impedance and loss tangent spectra of the samples have been evaluated by establishing a correlation between NRP and the inductive character of the ceramics. The dc conductivity and the real component of complex impedance analyses imply the semiconducting nature and the negative thermal coefficient (NTC) of resistance of the ceramics. Ac conductivity analyses also indicate a pre-dominant CBH charge transport mechanism in the ceramics except for EuBa2Cu3O6.5.

Relaxation behavior at high temperature associated with oxygen vacancy in the Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics

Dielectric relaxation behavior and conductiviy of Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics prepared by conventional solid-sate reaction method were investigated. With the introduction of the (LiCe), the conductivity was improved significantly and the large conductivity at high temperature (∼10−4 S·cm−1 at 530 °C) could be obtained. Phase transition from normal ferroelectric to relaxor-like ferroelectric was detected in the Sr1-x(LiCe)x/2.5Bi2Nb2O9 ceramics. Results of the complex impedance analysis indicated that the concentration of charge carriers increased gradually with the increase in (LiCe). Oxygen vacancy was confirmed to be responsible for the conductivity at high temperature by calculating activation energy of the carriers in the corresponding range of high temperature. Dielectric relaxation behavior at high temperature was attributed to the short-range conductivity of oxygen vacancies under thermal stimulation.

Structural, dielectric and complex impedance analysis of Pb-free BaTiO3-Bi(Mg0.5Ce0.5)O3 ceramics

(1–x)BaTiO3–xBi(Mg0.5Ce0.5)O3 (0.00 ≤ x ≤ 0.10) ceramics were prepared via a solid-state sintering route to investigate their structural, dielectric, impedance and energy storage properties. Phase analysis revealed tetragonal to pseudo-cubic phase transition in compositions with x ≥ 0.06. Doping of BaTiO3 with Bi(Mg0.5Ce0.5)O3 decreased the average grain size from ≥ 10 µm to submicron level which decreased the electrical conductivity and increased the electrical breakdown strength up to 250 kV cm−1. The observed decrease in bulk resistance with an increase in temperature demonstrated a typical negative temperature coefficient of resistance-type behavior for these ceramics. The x = 0.08 composition exhibited a high energy storage density (∼1.84 J cm−3) with a recoverable energy density (∼1.26 J cm−3) and an electrical breakdown strength ∼250 kV cm−1. The obtained results demonstrate that this ceramic can be considered to be a good candidate for application in advanced pulsed power capacitors.

New linear high-temperature thermistors based on the xAl2O3-(1-x)CaMnO3 ceramics

It is very important for a thermistor to have linear electrical properties, which can effectively reduce the complexity of circuit design. Phase structure modulation through introducing a second phase is crucial to achieve high performance electronic ceramics. Herein, new linear high-temperature thermistors based on the xAl2O3-(1-x)CaMnO3 ceramics were synthesized by the solid phase reaction method. With increasing Al2O3 content, CaMn2O4 and CaAl2O4 phase were observed, which formed internal conducting network and induced linear electrical properties. The ceramics exhibited negative temperature coefficient (NTC) thermistor characteristics in the temperature range of 523 K–1173 K. Their resistance-temperature (R-T) relationship displayed a good linear characteristic, especially for x = 0.3, which showed the highest linearity (R2: 0.9984) in the temperature range of 523 K–1173 K, covering medium to high temperature region. The mechanism of linear electrical properties was explained by a parallel conductive model in combination with complex impedance analysis. This approach could be generalized for designing linear high-temperature thermistors with a wide temperature range.

Optimal design of broadband acoustic metasurface absorbers

The absorption of low-frequency noise has always been limited by structural thickness, but the novel physical properties of sound-absorbing metamaterials provide a solution to this problem. Based on genetic algorithm, an acoustic metasurface absorber (AMA) composed of micro-perforated plates (MPPs) and impedance matching coiled-up cavities (IMCCs) is proposed. Different from previously reported metamaterials, this structure can easily provide flexible and accurate broadband sound absorption in different target frequency bands. The theoretical model behind the algorithm is established, and two optimal structures (AMA I/AMA II) are obtained for low and mid-high frequency bands. Broadband sound absorption is realized with a thickness of only 71 mm (about 1/13 of the relevant wavelength at 369 Hz), and an average sound absorption coefficient of 0.931 is achieved in the low-frequency band of 350–1000 Hz. Furthermore, by changing the frequency band of the quasi-perfect absorber to 500–2000 Hz, the average sound absorption coefficient exceeds 0.945 with a thickness of only 55 mm (about 1/11 of the relevant wavelength at 563 Hz). The reflection coefficient in the complex plane and theoretical impedance analysis are utilized to reveal the underlying mechanism of the absorption and the acoustic characteristics of the two structures, which show excellent broadband absorption performance in the low and mid-high frequency bands. This work provides a method of arbitrarily modulating surface acoustic impedance in broadband and a reference for broadband noise control.

Complex Impedance and Modulus Analysis on Porous and Non-Porous Scaffold Composites Due to Effect of Hydroxyapatite/Starch Proportion.

This study aims to investigate the electric responses (complex modulus and complex impedance analysis) of hydroxyapatite/starch bone scaffold as a function of hydroxyapatite/starch proportion and the microstructural features. Hence, the non-porous and porous hydroxyapatite/starch composites were fabricated with various hydroxyapatite/starch proportions (70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 10/90 wt/wt%). Microstructural analysis of the porous hydroxyapatite/starch composites was carried out by using scanning electron microscopy. It shows that the formation of hierarchical porous microstructures with high porosity is more significant at a high starch proportion. The complex modulus and complex impedance analysis were conducted to investigate the electrical conduction mechanism of the hydroxyapatite/starch composites via dielectric spectroscopy within a frequency range from 5 MHz to 12 GHz. The electrical responses of the hydroxyapatite/starch composites are highly dependent on the frequency, material proportion, and microstructures. High starch proportion and highly porous hierarchical microstructures enhance the electrical responses of the hydroxyapatite/starch composite. The material proportion and microstructure features of the hydroxyapatite/starch composites can be indirectly reflected by the simulated electrical parameters of the equivalent electrical circuit models.

Impact of two-step calcination on microstructure, phase, electronic, and dielectric properties of KCa2Nb3O10 bulk layered perovskite

ABSTRACT The effects of varying calcination temperature, K content, and the number of calcination steps in the dielectric performance of KCa2Nb3O10 synthesized via solid-state reaction are investigated. Adding an extra calcination step at 500°C followed by another calcination at 1100°C suppressed the formation of secondary phases while maximizing the relative density (95%) and the average grain area (2.12 μm2). The first calcination at 500°C ensures the formation of intermediate phases (KNbO3 and Ca2Nb2O7), which are prerequisites for single-phase KCa2Nb3O10 synthesis. A significantly high dielectric constant of 352 at 100k Hz is achieved in the two-step calcined sample despite the low sintering temperature of 1250°C. The highest resistivity of the two-step calcined sample (2 × 108 Ω cm) obtained from complex impedance analysis supports its lowest dielectric loss (0.034 at 100k Hz). When the two-step calcined KCa2Nb3O10 powder is exfoliated, much higher dielectric properties of Ca2Nb3O10 nanosheets are expected.

Low-temperature dielectric and impedance properties of Ba1-xSrxTiO3 and BaTi1-xTaxO3 ceramics

In this work, two series of BaTiO3-based ceramics, Ba1-xSrxTiO3 (x = 0, 0.2, 0.4, 0.6, 0.8) and BaTi1-xTaxO3 (x = 0.03, 0.06, 0.075, 0.09, 0.1), were synthesized by using standard solid-state reaction method at 1350 ?C, and then sintered at 1400 ?C for 10 h in air. Frequency-dependent dielectric and impedance properties were investigated at low temperature range of 100-300K. The changes in dielectric properties of the Ba1-xSrxTiO3 ceramics are believed to originate from the phase transition due to the different A-site Sr2+ doping concentration. The local electron-pinned defect-dipole effect is responsible for the enhancement of dielectric constant observed in the B-site Ta5+ doped BaTi1-xTaxO3 ceramics. The complex impedance analysis was used to discern the temperature and frequency dependence of grains and grain boundaries responses. The results suggest that A- and B-site doped BaTiO3 ceramics can be applied for different dielectric devices at low temperatures.

Investigation on optical, structural and electrical properties of solid-state polymer nanocomposites electrolyte incorporated with Ag nanoparticles.

A solid polymer electrolyte based on polyvinyl alcohol (PVA)/carboxymethyl cellulose (CMC)/polyethylene 3,4-dioxythiophene: sodium polystyrene sulfonate (PEDOT:PSS) has been prepared with various concentrations of incorporated silver (Ag) nanoparticles (NPs) by using solution cast approach. The FTIR spectroscopic study revealed the complexation between the polymeric nanocomposite (PNC) and the Ag NPs. The X-ray diffraction (XRD) results infer that the semicrystalline phase of PNC decreases as the amount of incorporated Ag NPs increases. The transmission electron microscope (TEM) image revealed that Ag NPs have diameters ranging from 22 to 43nm. Complex dielectric permittivity and alternating current (AC) electrical conductivity of nanocomposite films have been investigated in the frequency range from 0.1Hz to 20MHz at 30°C. Dc conductivity ([Formula: see text]) values for the nanocomposite films are estimated from AC conductivity plots. The [Formula: see text] value was observed to increase from 1.98 × 10-9 to 2.29 × 10-7S.cm-1 for the PNC system incorporated with optimal Ag NPs. From complex impedance (Z*) analysis, it has been found that the bulk electrical resistance (Rb) of the PNC films decreases with increasing the Ag NPs content. Therefore, these obtained PNC films have promising applications in energy storage devices.

Synthesis and complex impedance analysis of nano cubic CH3NH3SnI3 perovskite for the development of optoelectronic lead-free Schottky diode

The synthesis of a lead-free tin-based perovskite material is a crucial step toward developing a sustainable energy device. However, the oxidation of Sn2+ to Sn4+ during synthesis in an open atmosphere is the basic synthetic problem in tin-based perovskites. In this study, a modified technique for nanoparticle synthesis was applied to submerge the oxidation issues and synthesised nano cubic tin-based hybrid CH3NH3SnI3 perovskite in the glove box in an inert environment (N2) to make the Schottky device. The crystallinity of the synthesised perovskite sample was confirmed by PXRD. The structural parameters such as crystalline size (D), dislocation density (δ), strain (ε), and the lattice parameter were calculated from the XRD pattern and were found to be 62.90 nm, 2.52 × 1014 nm−2, 6.12 × 10−3 lin−2/m−4, and 6.23951 Å, respectively. The material was characterised by UV–Vis. spectroscopy, TGA, FESEM, and EDX measurements. The frequency-dependent transport properties of this perovskite sample were investigated using complex impedance spectroscopy (CIS) in the frequency range of 4 Hz–8 MHz. The conductivity relaxation time, DC conductivity, and AC conductivity were calculated as 6.45 × 10−5 s, 2.01 × 10−6 S/m, and 6.98 × 10−4 S/m, respectively. A Schottky device was fabricated using this perovskite. Excellent performance of this device was observed from its electrical characterization in terms of conductivity both in the dark (1.04 × 10−6 S/m) and light (1.96 × 10−6 S/m) conditions. So, this work will be very beneficial to the further development of the lead-free CH3NH3SnI3 perovskite and its subsequent electrical applications.

Development of high‐performance biopolymer nanocomposites derived from carboxymethyl chitosan/boehmite via green synthesis

AbstractIn this work, biopolymer nanocomposites derived from carboxymethyl chitosan (CMCS) and boehmite were prepared via an environmentally friendly technique and their structural, morphological, thermal, electrical, dielectric, and mechanical properties were investigated. The successful fabrication of carboxymethyl chitosan/boehmite nanocomposites was evident from the appearance of characteristic peaks of boehmite in FTIR and alteration in the morphology as revealed by optical and SEM micrographs. The glass transition temperature (Tg) and melting temperature (Tm) were increased as the filler content increased. The enhanced thermal stability of nanocomposites was clear from thermogravimetric results. The incorporation of boehmite nanoparticles into CMCS improved the conductivity to a semiconducting range. The dielectric constant of CMCS/boehmite nanocomposites was significantly higher compared to pure CMCS. The influence of temperature on AC conductivity, activation energy, dielectric constant and loss tangent were analyzed. Complex impedance analysis carried out by Nyquist plots and the bulk resistance showed a decreasing trend with temperature, which indicated enhanced conductivity with temperature. Tensile strength and hardness were observed to be increased with boehmite inclusion, whereas elongation at break is reduced. As a result, eco‐friendly CMCS/boehmite biopolymer nanocomposites with good thermal, mechanical, electric, and dielectric properties may be a potential green alternative for flexible electronic, charge storage, and other electrochemical devices.

Colossal dielectric response and complex impedance analysis of LaFeO3 ceramics

The present investigations mainly focused on the colossal dielectric response and complex impedance analysis of LaFeO3 ceramics. The studied sample was prepared by a citrate gel method. Structural and microstructural properties are analyzed from the XRD pattern and SEM micrograph. The anomalies in the dielectric constant versus temperature plots are analyzed on the basis of polarization induced by the Maxwell-Wagner mechanisms and ferromagnetic interaction between the Fe[Formula: see text] ions driven by the oxygen vacancy mediated Fe[Formula: see text]–V[Formula: see text] –Fe[Formula: see text] exchange interaction A giant dielectric permittivity in the order of [Formula: see text]105 was observed in the sample even at the room temperature for 100 Hz. The colossal dielectric constant in LaFeO3 is mainly driven by the internal barrier layer capacitor (IBLC) formation. The formation of IBLC was explained on the basis of highly insulating grain boundary and less resistive/semiconducting grain, which was confirmed from both the resistance and capacitance of grain and grain boundary from the impedance analysis. The non-Debye-type relaxation process associated with the grain and grain boundary effect was investigated from the broad and asymmetric relaxation peak. The relaxation time for both the grain and grain boundary effect was also calculated. In addition to this, we have also analyzed the normalized bode plot of imaginary part of impedance and electrical modulus which suggests the relaxation process dominated by the short-range movement of charge carriers.

Analysis of frequency dependence of complex impedance and electrical characterization of Fe2O3/kaolin ceramics for civil engineering applications

The complex impedance spectroscopy (CIS) method is usually used in order to analyze the electrical response of different semiconducting disordered materials as a function of frequency at different temperatures. The real and imaginary parts of the complex impedance can show different semicircles in the complex plane that give evidence for the presence of both bulk and grain boundary contributions. Many parameters can be deduced from the analysis of CIS data, such as relaxation times and activation energies. There are some literature data concerning electrical properties of clays and (semiconductor, sand, cement,…)/clay mixtures. Most of the published works are related to the AC conductivity of rocks with the effect of water or oil content but there are no similar studies on the characterization of the microstructure of individual clays as ceramic materials by analyzing their temperature and frequency dependence of their electrical conductivities. Hence, this paper presents an analysis of electric complex impedance of the Fe2O3/Kaolin composite in the high temperature range up to 740 °C. Sinusoidal voltage with frequency in the range [100 Hz, 1 MHz] is applied to the material in order to measure the electrical conductivity for various concentrations of Fe2O3 from zero to 100 %. The activation energies for the conduction and for the relaxation processes are determined and their dependence on the density of Fe2O3 analyzed. Furthermore, let’s found that Fe2O3 have the effect to increase the electrical conductivity in our samples. From the Nyquist diagrams, only one semi-circle related to the contribution of the grains to the total electrical conduction is identified for all investigated samples.

Analysis of complex impedance and electrical conductivity of YCr0.5Mn0.5O3–CaCu3Ti4O12 negative temperature coefficient ceramics

YCr 0.5 Mn 0.5 O 3 (YCM)-CaCu 3 Ti 4 O 12 (CCTO) ceramics were prepared using a solid processing method, and their properties were studied. XRD measurements showed that all prepared ceramics had pure perovskite structures. With increasing YCM content, grain size in ceramics decreased, and the resistivity of materials was found to be very sensitive to grain size and grain size distribution. Moreover, ceramics had NTC characteristics, and values of ρ 25 , B 25/75 , and E a ranged from 2.21 × 10 6 –7.30 × 10 6 Ω cm, 5797–6300 K, and 0.5390–0.5800 eV, respectively. The presence of heterovalent ion pairs in samples suggested that conduction mechanism may have been related to electron hopping. Impedance spectroscopy results showed that excessive doping with YCM resulted in greater contribution from grains to overall resistance of the material. Temperature-dependent electrical relaxation behavior was dominated by short-range movement of charge carriers.

Complex impedance, dielectric constant, electric modulus, and conductivity analysis of Cd doped ZnO nanostructures at high temperatures

Cd-doped zinc oxide (ZnO) nanostructures with a standard formulation Z n ( 1 − x ) C d x O (x = 0%, 3%, 6%, and 10%) were fabricated by a co-precipitation technique. The structural and morphological analyses were studied using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The Study of x-ray diffraction investigation indorses the existence of a wurtzite structure with a P 6 3 mc space group in all the samples. Impedance spectroscopy, dielectric measurements, and electrical conductivity at different temperatures of 300–460 K with a frequency range from 20 Hz to 2 MHz were performed using an impedance LCR meter. The complex impedance spectrum ( Z ´ ´ v s Z ´ ) for all samples were fitted with a parallel bulk resistance ( R b ) and capacitance ( C b ) combination circuit. The results of the dielectric measurements indicate that the parameters ε ´ , ε ´ ´ , and tanδ are reduced with the increasing frequency and increase with temperature. The complex electric modulus plots ( M ´ , M ´ ´ ) with frequency have explained the non-Debye type of relaxations mechanism due to interfacial and depolarization. The variation of ac ( σ a c ) conductivity with Cd concentration indicates a gradual increase because the impedance values with Cd-doped decrease. It is confirmed that the activation energies decrease with the doping of Cd concentration. Moreover, ac conductivity was then investigated by Jonscher's power law. Finally, the temperature-dependent exponent s fitted well with the correlated barrier hopping (CHB) conduction. • Cd-doped ZnO nanoparticles with different concentrations were fabricated by the co-precipitation method. • XRD studies revealed the incorporation of Cd into ZnO lattice. • Nyquist plots suggested the negative temperature coefficient of resistance behaviour. • The influence of Cd-doping on the electrical behaviour of ZnO was reported.

Structural and Impedance Analysis of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 Ceramic

Background: Since (1-x)[Pb(Mg1/3Nb2/3)O3]-(x)PbTiO3 (PMN-PT) ceramic has a high dielectric constant and piezoelectric coefficient, it has been widely investigated for profound applications in electro-optical devices, sensors, multilayer capacitors and actuators. Objectives: The objective of this paper is to study the structural and electrical properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (0.7PMN-0.3PT) ceramic to understand the biphasic structural nature using Rietveld Refinement. Also, it characterises the type of conduction process as well as the role of grain and grain boundary resistance in the material on the basis of electrical properties such as impedance and modulus to understand the relaxation process. Methods: 0.7PMN-0.3PT is synthesised by mixed oxide method using PbO, MgO, Nb2O5 and TiO2 as precursor materials. Results: The XRD data reveals the biphasic structure of the tetragonal phase with the space group of P4mm and the monoclinic phase with the space group of Pm. The complex impedance analysis clearly represents the effect of grain on the overall resistance and departs from normal Debye-type behaviour. Also, the resistance is found to decrease with temperature, thereby confirming the semiconducting nature of the sample. The presence of long as well as short-range mobility of charge carriers is confirmed from the modulus and impedance analysis. The influence of long-range motion is observed at high temperatures and of short-range motion at low temperatures. Conclusion: XRD analysis confirmed the biphasic structure of the M+T phase. The frequencydependent modulus and impedance spectroscopy show the presence of a relaxation effect in the ceramic which is found to increase with temperature. The Nyquist plot shows that the resistance is decreased with temperature, thereby confirming the NTCR behaviour in the studied sample.

Electrical conductivity of siderite and its implication for high conductivity anomaly in the slab-mantle wedge interface

Carbonate minerals as a dominant carbon host can be transported to the Earth’s deep interior via subduction of the oceanic lithosphere, and their physicochemical behavior potentially has a significant influence on the compositional heterogeneity and physical properties in the deep mantle. In this study, we measured the electrical conductivity of natural siderite at 1–3 GPa and 100–700°C using a complex impedance analyzer in a large volume multi-anvil high-pressure apparatus. A sharp increase in conductivity was observed at ∼400°C under various pressures, and subsequently, the electrical conductivity keeps anomalously high values in the whole temperature range owing to a small quantity of interconnected highly conductive phases (graphite and magnetite) produced from the low degree decarbonation of siderite. The change in electrical conductivity and activation enthalpy suggest that the conduction mechanisms before and after low degree decarbonation of siderite are the small polaron (electron hopping in Fe2+–Fe3+) and highly conductive phases, respectively. Our results indicate the incipient decarbonation temperatures at 1–3 GPa are considerably lower than the decomposition boundary of siderite determined by phase equilibrium experiments, implying the initial decarbonation reaction of Fe-bearing carbonates in the subducting oceanic crust occurs at a shallower depth. The 30 vol.% of siderite is required to enhance the electrical conductivity of (Mg, Fe)CO3 solid solutions. Magnetite and graphite generated from the decarbonation reaction of the siderite component of Fe-bearing carbonate make a significant contribution to the high conductivity anomaly observed in the slab-mantle wedge interface.

Investigation of the structural, optical, electrical and dielectric proprieties of LiCd0.5Fe2O4 spinel ferrite

The spinel ferrite material families are subjected to diverse studies according to their wide field application. In this work, the LiCd0.5Fe2O4 ferrite was successfully synthesized by a conventional solid-state method. The structural, optical, electrical and dielectric characterizations were treated. The Rietveld refinement method explored cubic spinel structure (Fd3‾m space group) with a lattice parameter: a = 8.628 Å, α = 90°. Besides, the surface micrograph shows a strong agglomeration of the grains. Optical results were calculated using diffuse reflectance data and Kubelka Munk theory. They show the semiconductor nature with a band gap around 2.9 eV and Urbach energy around 0.14 eV.The electrical measurements were studied over a range of frequency (40 Hz–1 MHz) and through large temperature scale (200 K–380 K) using the complex impedance spectroscopy technique. The AC conductivity behavior was described by the jump relaxation model, which obeys to the Jonscher's law. The complex impedance analysis has suggested the presence of the contribution of the grains, the grain boundaries and interface in the conduction mechanism. A reduction in real part Z′ was observed as a function of temperature and frequency, which indicates an increase in ac conductivity and a negative temperature coefficient of resistance. Hence, the complex modulus plots have affirmed the presence of grain boundaries contribution in the material. Both the complex modulus and impedance investigations have confirmed that the synthesized material exhibits a non-Debye type of relaxation. Finally, the dielectric behavior of the studied sample shows a polarization effect and the permittivity graphs are fitted theoretically with the Cole-Cole model.

Effect of the substitution of titanium by niobium on the structural, electric and modulus properties in Ba0.97La0.02Ti(1-x)Nb4x/5O3 perovskites

Ba0.97La0.02Ti0.93Nb0.056O3 (illustrious as BLT0.93Nb0.056) novel lead-free sample was elaborated using the molten-salt reaction means. This polycristalline ceramic was checked by X-ray diffraction (XRD) at room-temperature (at RT), as well, the electric measurements over a broad temperature (T) and frequency (f) sequences. XRD pattern revealed a single-perovskite phase crystallized in a tetragonal system with P4/mmm space group. The electrical properties of the compound, deduced from the complex impedance analysis show a strong dependence on frequency (f). The EIS (Electrochemical Impedance Spectroscopy) data exhibited an approximately perfect semi-circle at elevated temperature in the complex plane plot as well as a practically ideal non-Debye peak shape in the spectroscopic plot. The semicircle arc specifies the existence of a frequency relaxation (fmax) as well as a time relaxation (τ). These results could help understand the relationship linking the structure and the electrical properties of BLT0.93Nb0.056.