Non-overlapping Small Polaron Tunneling Model Research Articles

Electrical conductivity and relaxation mechanisms of nanocrystalline Ba0.75Ca0.2Cs0.05TiO3

Ca and Cs doped barium titanate lead-free ceramic with the formula Ba0.75Ca0.2Cs0.05TiO3 has been prepared by the solid-state reaction method. X-ray diffraction (XRD) confirms the crystallization of the sample in a tetragonal structure with a P4mm space group. The phase purity and grain morphology were evaluated using X-ray diffraction and scanning electron microscopy (SEM). The material exhibits a primary phase of Ba0.75Ca0.2Cs0.05TiO3 with a minor secondary phase of BaO2, and the average grain size is determined to be 1.66 μm. Using non-destructive complex impedance spectroscopy (CIS), we extensively studied the electrical behavior, including complex impedance (Z*), complex modulus (M*), electrical conductivity, and relaxation mechanisms, of Ba0.75Ca0.2Cs0.05TiO3 over a wide temperature (85 K–290 K) and frequency range. The ac conductivity analysis reveals that the dominant conduction mechanism is the non-overlapping small polaron tunneling (NSPT) model. The impedance analysis indicates a single semi-circle in the real and imaginary parts, suggesting a single relaxation mechanism. Additionally, the activation energy was calculated to be approximately 0.0489 eV. These findings contribute to the understanding of the structural and electrical properties of Ba0.75Ca0.2Cs0.05TiO3, highlighting its potential applications in electronic devices such as capacitors, thermistors, and ferroelectric random access memories (FRAMs).

Temperature and frequency dependence of conductivity, density of states, and dielectric permittivity of ternary metal chalcogenide PbSnSe2 flake

The mechanically cleaved flake of ternary metal chalcogenide PbSnSe2 was transferred onto the interdigitated electrodes to form electrical contacts. The temperature dependent (180 K–250 K) electrical properties were then analyzed employing complex impedance spectroscopy from 2 kHz to 2 MHz. A detailed analysis of Nyquist plots proposed the space charge dependent behavior and negative temperature coefficient of PbSnSe2 flake. The AC conductivity followed Jonscher's power law with s-parameter value being less than unity. The values of s-parameter increased with rise in temperature suggesting the presence of non-overlapping small polaron tunneling (NSPT) in the PbSnSe2 flake. From this NSPT model, tunneling distance, hopping energy, and density of states (DOS) were estimated at temperatures from 180 K–250 K. The dielectric permittivity showed dispersion at lower frequencies and the tangent loss was also found to be directly related to temperature. A single semicircular arc in complex modulus analysis showed the dominance of bulk effect in the material.

Structural, morphological, optical, magnetic and impedance spectroscopic properties of Ni0·5Fe2·5O4 nanoparticles synthesized by the self-combustion method

The synthesis of Ni0·5Fe2·5O4 nanoparticles was successfully carried out by the self-combustion method using glycine as fuel. Analysis of the XRD measurements indicates the formation of a cubic spinel monophase with the space group (Fd-3m) and a nanometric crystallite size. According to the optical study, this sample shows strong absorption in the visible range with a gap energy of 3.7 eV, making it a good candidate for optoelectronic and photovoltaic applications. Complex impedance spectroscopy was carried out in the temperature range 300–480 K with the frequency varying between 40 Hz and 5 MHz. The frequency dependence of the dielectric constant was explained in terms of charge carrier transport between Fe2+ and Fe3+, while its temperature dependence indicates dielectric relaxor behavior. The scaling law shows a perfect superposition of impedance and modulus spectrum in the temperature range studied which confirms that the increase of temperature does not bring any change on the mechanism of relaxation. For the electrical properties, the conductivity study shows a semiconducting behavior with a predominance of the Non-Overlapping Small Polaron Tunneling (NSPT) model over the conduction process. The dc conductivity and jump frequency are positively correlated by the extracted activation energies. Summerfield scaling leads to the superposition of the conductance spectra into a single main curve, confirming the validity of this approach. The low value of the dielectric loss and the high value of the permittivity at room temperature and at low frequencies make this sample a potential candidate for energy storage and microwave devices. In addition, the dependence of the magnetisation on the applied magnetic field has been studied in depth by adjusting the hysteresis cycle by different laws of the saturation approach.

Synthesis, crystal structure, BFDH morphology, Hirshfeld surface analysis and electrical characterization of the new bi-(2-amino-5-methylpyridinium) hexa-chlorostannate compound

The Organic–inorganic hybrid compounds have attracted considerable attention for their scientific and technological potential according to their wide field application. In this paper, we describe the preparation of a new hybrid crystal, with the structural formula [C6H9N2]2SnCl6, of which crystallographic, BFDH morphology, Hirshfeld and complex impedance spectroscopy have been studied and analyzed. The X-ray diffraction analysis revealed that the title compound crystallized in the centrosymmetric space group P21/c of the monoclinic system. The powder XRD is used to confirm the phase purity of the sample and the crystalline nature of the powder.The [C6H9N2]2SnCl6 crystal morphologies are simulated from the Laue symmetry (2/m), and from the space group symmetry (P21/c), which highlighted the effect of the screw axe 21 and the glide plane c in reducing the Importance morphology in the constructed model considering the space group symmetry. The intermolecular interactions studied using Hirshfeld surfaces showed the important contribution of H⋯Cl/Cl⋯H intercontacts (67.1 %) in the [C6H9N2]2SnCl6 crystal packing.The analysis of real and imaginary parts impedance spectra shows that the electrical properties are heavily dependent on frequency and temperature, indicating a relaxation phenomenon and semiconductor-type behavior. The Nyquist plot (-Z″ vs Z′) showed only one semicircular arc, representing the grain effect in the electrical conduction. The obtained results were analyzed by fitting the experimental data to an equivalent circuit model R/CPE/C. The Alternating current conductivity (σAC) follows Jonscher's power law. The latter confirmed that the conduction is insured by the non-overlapping small polaron tunneling model (NSPT) model, which has been studied in depth.

Structural, optical and electrical properties of NiMO4 (M=W and Mo)

The NiMO4 (M=Mo and W) samples have been synthesized using the solid-state reaction method at high temperatures. The structural, optical, and electrical transport properties were investigated. X-ray diffraction data refined via the Rietveld method showed the monoclinic system for these compounds. The UV/Vis optical spectra indicate that the direct gap energy values are 2.72 eV for NiMoO4 and 2.81 eV for NiWO4 compounds which can be promising candidates for semiconductor applications. These materials were characterized by an impedance spectroscopy technique measured in the 1 – 106 Hz frequency and 398 – 533 K temperature range. The AC conductivity was analyzed using the Jonscher power law, which showed that the conduction mechanisms are well described by the non-overlapping small polaron-tunneling model (NSPT) in phase I and the correlated barrier-hopping model (CBH) in phases II for the Mo-based compound. Moreover, the overlapping-large polaron tunneling (OLPT) model for the NiWO4 compound. The conduction mechanism was interpreted with the help of Elliot's theory, and the Elliot's parameters were determined. The comparative study of the two titled compounds shows better properties for the Mo-based compounds.

Crystal structure, thermal behavior and electric properties of a new semiconductor cobalt-based hybrid material

The crystals of the new organic-inorganic hybrid material, (C5H12N)2[CoBr2.73Cl1.27], were successfully synthesized by the slow evaporation method and characterized by single-crystal X-ray diffraction, thermal analysis, UV–Vis absorption and electrical measurements. This compound crystallizes in the centrosymmetric space group P21/n of the monoclinic system with unit cell parameters: a = 9.7724 (6) Å, b = 12.3920 (6) Å, c = 15.0307 (9) Å, β = 100.864(6) °, V = 1787.59(18) Å3 and Z = 4. The IR spectrum of the compound is studied, especially for the cationic vibrational part. The thermal analysis indicates that (C5H12N)2[CoBr2.73Cl1.27] is stable up to 270 °C and that it undergoes two reversible phase transitions at 152 and 187 °C and at 141 and 128 °C on heating and cooling, respectively. From UV visible gap energy value of 3 eV it can be concluded that the new mixed halide compound is a semiconductor material. The electrical behavior of (C5H12N)2[CoBr2.73Cl1.27] was studied using impedance spectroscopy in the temperature range of 323 to 403 K. According to a study on the frequency dependence of ac conductivity, the material follows Jonscher's universal dynamic law with an increase in the frequency exponent (s) as temperature increases. This behavior reveals that the conduction mechanism is the nonoverlapping small polaron tunneling (NSPT) model.

Low-frequency electrical response related to oxygen vacancies in Al3+ substituted M-type hexaferrite

The presence of oxygen vacancies is unavoidable in many complex metal oxide materials such as hexaferrites. This article investigates the role of crystal defects, such as oxygen vacancies, and different oxidation states of Fe ions, on the electrical conduction behaviors of Al3+ substituted Ba0.4La0.1Sr0.5Al x Fe12−x O19 hexaferrites by analyzing the temperature dependent AC impedance and AC conductivity. The optimal substitution of La3+ ions and high-temperature sintering is responsible for forming oxygen vacancies while reducing Fe from Fe3+ to Fe2+ cations, as observed in structural and XPS analysis, which affects electrical conduction behaviors. The departure from ideal Debye-type relaxation behavior is also one of the effects of crystal defects. Temperature variation of relaxation time shows a sharp change at around 403 K. This may be due to different electrical entities influencing the mode of electron hopping with temperature. The activation energy calculated from the temperature dependent relaxation time confirmed the presence of electron hopping through the bridging effects of the first ionization of oxygen vacancies Fe2+––Fe3+ below a temperature of 403 K. Above 403 K, electron hopping through different oxidation states of Fe3+ + e− → Fe2+ and migration of oxygen vacancies toward the bulk surface are responsible for the conduction mechanism. The DC resistivity and AC conductivity show that the bridging effects of oxygen defects can also induce Coulomb interaction between the defect sites resulting in Efros–Shklovskii variable range hopping and correlation barrier hopping below 403 K. Above 403 K, polaron-assisted electron hopping is more desirable, as confirmed by the non-overlapping small polaron tunneling model.

Structural study and temperature dependent relaxation and conduction mechanism of orthorhombic tungsten bronze Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic

In this study, the Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic was prepared using the solid-state technique. The X-ray diffraction technique was used in this study to investigate the Ba/La order in the solid solution Ba4La28/3(Zr0.05Ti0.95)18O54. We have developed a structural model, to represent the order within the structure. The formula of model [Ba4−a□a]A2[La8+2b3□2−2b3]A1,A1′(Zr0.05Ti0.95)18O54 is described as perovskite layers with a thickness of 3 octahedral parallel to the xOz plane. Scanning electron microscopy (SEM) showed that Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic exhibits a typical columnar grain with a heterogeneous distribution over the entire surface. Complex impedance spectroscopy was used to analyze the dielectric and electrical properties of Ba4La28/3(Zr0.05Ti0.95)18O54 materials over a frequency range of 10 Hz to 1 MHz and a temperature range of 350°C to 400°C. An appropriate equivalent electrical circuit was also used to investigate the contributions of grains and grain boundaries. The AC-conductivity data was analyzed using Jonscher's universal power law. The thermal behavior of the exponent parameter "s" indicates that the dominant conduction mechanism in our compound is the non-overlapping small polaron tunneling (NSPT) model. The activation energies calculated from the conduction and relaxation mechanisms are nearly identical for the Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic.

Temperature-driven complex dielectric and polaron-hopping mediated electrical conduction in aurivillius Gd2MoO6

In this work, aurivillius gadolinium molybdate (Gd2MoO6) was synthesized by the conventional solid-state route which was accompanied by cutting-edge characterization i.e., structural, and electrical, to give insight into the material characteristics required for possible high-temperature applications. The single-phase crystalline nature with monoclinic symmetry (C2/c, Space group-15) of Gd2MoO6 was confirmed by the X-ray diffraction (XRD) pattern. The average particle size was obtained to be ∼0.495 µm. The electrical conductivity and dielectric properties of a Gd2MoO6 plate capacitor were investigated in the frequency range between 10 Hz and 1 MHz and temperature from 473 to 773 K. A high dielectric constant (ε') of ∼3272 and low dielectric loss (δ) of ∼200 was observed at the low frequency and high-temperature regions, respectively. The Maxwell–Wagner interfacial polarization was found to be responsible for the decrease of the dielectric constant with increasing frequency. The behavior with the temperature of the frequency exponent (n) from the fitted conductivity spectra by Jonscher power law corresponds to the non-overlapping small polaron tunneling model between 473–673 K and correlated barrier hopping model at/over 673 K. The non-exponential Kohlrausch Williams-Watts function was introduced to fit the imaginary modulus (M′′) spectra and the activation energy was obtained to be 0.81 eV for grain and 0.94 eV for grain boundary conduction. The Nyquist plots(Z′vs.Z′′) differentiate the grain and grain boundary contribution and were fitted with the combinations of resistance (R), capacitance (C), and constant phase element (Q) in an equivalent circuit model(RC)(RCQ). Typical negative temperature coefficient of resistance behaviors of Gd2MoO6 suggest its possible application as thermistors in modern electronics circuits.

Physical insights into the grain size effect on the electrical properties of nanocrystalline La2Zr2O7 pyrochlores

The role of grain size on the electrical properties of nanocrystalline La2Zr2O7 (LZO) ceramics prepared by chemical co-precipitation is reported. Grain size from 10 to 70 nm was obtained. The XRD and Raman scattering showed a pyrochlore structure of La2Zr2O7. Morphology and chemical analysis were done by SEM and XPS, respectively. Electrical conductivity studies using impedance spectroscopy resolved the conductivity borne to grain and grain boundary with a non-Debye nature of conduction. The activation energy (Ea) for electrical conduction through grain was almost the same for all the grain sizes and equal to 1.20 ± 0.03 eV. However, the Ea of the grain boundary had decreased from 1.17 eV to 0.78 eV with an increase in grain size, and the conduction is due to oxygen ion migration. The conduction mechanism was governed by the non-overlapping small polaron tunneling model. Additionally, ion-ion correlation in conduction is increased with increasing grain size.

Implementing a sol-gel route to adjust the structural and dielectric characteristics of Bi and Fe co-doped BaTiO3 ceramics

The present work explores the impact of Fe insertion on the physical properties of Ba0.95Bi0.05Ti1-xFexO3 (x = 0.025, 0.050, and 0.075) prepared via sol gel method. The resulting samples crystallize in the tetragonal structure with space group P4mm and their morphological features point out the variation of the microstructure with Fe content. In turn, the dielectric constant versus temperature plot reveals the existence of two transition phases: the first one is ferroelectric-paraelectric transition phase (TF-P) and the second one is ferroelectric orthorhombic - ferroelectric tetragonal phase (TO-T). Analysis of conductivity curves using Jonscher’s augmented equation (for x = 0.025) and Jonscher’s power law (for x = 0.075) suggests the Non-Overlapping Small Polaron Tunneling (NSPT) model as a conduction mechanism.

Dielectric Properties of Polyaryletherketone/CaCu3Ti4O12 Nanocomposite Films Fabricated via Cast Film Extrusion Process

Polymer composites prove to be the best choice for improving the dielectric properties of polymers. This work mainly focuses on studying the dielectric behavior of polyaryletherketone (PAEK), a high-temperature polymer, and its nanocomposite films with CaCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Ti <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> (CCTO) ceramics. The dielectric constant of PAEK improves significantly after the addition of CCTO nanoceramics and shows nearly frequency-independent behavior. The dielectric loss of these nanocomposites is low and is in the range of 0.004–0.006 at room temperature and 1 kHz. Dielectric properties exhibit very good temperature stability up to 150 °C. Activation energies calculated from both electric modulus and conductivity analyses show that the movement of charge carriers is responsible for both relaxation and conduction processes. The conductivity mechanism follows the correlated barrier hopping (CBH) model at low temperatures and the nonoverlapping small polaron tunneling (NSPT) model at high temperatures. Breakdown characteristics are analyzed using Weibull probability distribution. These PAEK/CCTO nanocomposites are proposed as potential materials for high-temperature dielectric applications.

AC conductivity and electrical relaxation of a promising Ag2S-Ge-Te-Se chalcogenide glassy system

In this study, we developed a chalcogenide glassy system comprising (Ag2S)x-(0.4Ge-0.3Te-0.3Se)1-x, where x = 0.05, 0.10, and 0.20. The formation of Ag2S and GeSe2 nanocrystallites with small sizes and the development of GeTe, Ag2GeS3, TeS, and Se5.95Te1.05 phases with high Ag2S contents were confirmed by X-ray diffraction. The Fourier transform-infrared spectra demonstrated the characteristic vibration of Ag–S at 500–600 cm−1. Kinetic analysis of conductivity suggested that the Meyer–Neldel energy was due to polarons hopping from trap to trap induced by multiple phonon excitation. Tunneling of polarons through the grain boundary when x = 0.1 could be interpreted based on the modified non-overlapping small polaron tunneling model. By contrast, the correlated barrier hopping model was more appropriate for explaining the dominant conduction mechanism when x = 0.05 and 0.2. The lower relaxation times when x = 0.05 and 0.2 indicated a higher rate of polaron hopping. The temperature independence of the relaxation process was confirmed based on the scaling process.

Impedance spectroscopic study of charge transport and relaxation mechanism in the lead-free hybrid perovskite CH3NH3CuCl3

In the field of commercialization, organic–inorganic hybrid perovskite materials are becoming more popular these days in view of their prospective use in solar cells and also in other optoelectronic applications. In this paper, a non-toxic CH3NH3CuCl3 (MACuCl3) hybrid perovskite is successfully synthesized via the slow evaporation solution growth technique. The monoclinic phase of the material is checked using the X-ray diffraction measurement. The chemical composition of the prepared compound is discussed by a scanning transmission electron microscope coupled with the energy dispersive X-ray spectroscopy (STEM-EDS). Such systematic characterizations as differential scanning calorimetry (DSC) measurements and dielectric measurements indicate that MACuCl3 goes through a reversible phase transition at T1 ≈ 350/352 K MACuCl3 demonstrates a semiconducting property with a direct band gap value of approximately 2.54 eV. Over the 10−1-106 Hz frequency range, the dielectric constant, the loss factor, the electric modulus and also the electrical conductivity of MACuCl3 show strong temperature dependence. The Nyquist plot confirms the various contributions of grains and grain boundaries to the total impedance. In the high-frequency region, the dielectric constant tends to increase with temperature. The modified Cole–Cole plot asserts that while the relaxation time decreases with the rise in temperature, the space charge and free charge conductivity increase the moment the temperature climbs. In accordance with the modified Kohlrausch-Williams-Watts (KWW) equation, an asymmetrical nature corresponding to the non-Debye type of the perovskite is noticed in the electric modulus spectra at different temperatures. Moreover, the imaginary part of the electric modulus spectra is found to shift from the non-Debye toward the Debye type with the increase in temperature despite not getting the exact Debye response and emerging as a semi-conductor material. The study of the charge transfer mechanism of MACuCl3 is carried out based on Elliott's theory. The conduction mechanism in MACuCl3 is interpreted through the following two approaches: the overlapping large polaron tunneling (OLPT) model (phase 1) and the non-overlapping small polaron tunneling (NSPT) model (phase 2). Moreover, the high dielectric constant of MACuCl3 which is associated with a low dielectric loss makes it a possible candidate for energy harvesting devices.

Temperature dependent electrical transport behavior of (100-x)Bi2O3-x(BaTiO3) glass system

Impedance measurements were performed as a function of temperature (RT to 700 K) in the frequency range (1 Hz-1MHz) on fabricated Bismuth Barium Titanate glass samples. Dielectric permittivity is found to be increased on increasing both the temperature and BaTiO3 (BT) content in highly polarizable glass matrix of Bi2O3. Experimental data obtained for imaginary part of electric modulus (M″)has been fitted theoretically using non-exponential Kohlrausch-Williams-Watts (KWW) function, however Jonscher's universal power law has been employed to analyze the frequency dependent ac conductivity. The calculated activation energy values for both the samples have been found to be in close agreement with each other and qualify for doubly ionized oxygen vacancies, proposing that the similar kind of charge carriers are involved in the relaxation and conduction mechanisms. Stretched exponent (β) of Modulus and power exponent (n) of ac conductivity, estimated from theoretical fitting of experimental data, have been found to be dependent on temperature and BT (BaTiO3) content. On increasing temperature, an increase in values of (n) suggests that non-overlapping small polaron tunneling (NSPT) model can be easily applied to explain ac conduction and hopping transport mechanisms of the fabricated glass samples.

The lithium-ion battery: Study of alternative current conduction mechanisms on the Li3PO4 - based solid electrolyte

Lithium-ion batteries have been dominating as a power source in digital cameras, laptop computers, mobile phones and electric/hybrid electric vehicles. This can be explained by their high life cycle and power density which differentiate them from other battery types. Lithium phosphate is considered among the favored solid electrolyte materials for the lithium-ion battery because of its high ionic conductivity. In this study, Lithium phosphate (Li3PO4) compound was obtained by the classic ceramic method. The X-ray powder diffraction pattern indicates that at room temperature, Li3PO4 crystallized in the orthorhombic system with Pnma space group. The morphology and composition of Li3PO4 were performed by scanning transmission electron microscope coupled with energy dispersive X-ray spectroscopy (STEM-EDS). Infrared spectroscopy was confirmed the presence of (PO4)3− anion and its vibrations. The measurements of the electrical properties were performed in the 100 Hz to 1 MHz frequency range and 528–713 K temperature intervals. The interpretation of Nyquist curves revealed the presence of three electrically active areas equivalent to the electrode processes, distribution of grain boundaries and bulk mechanism. The alternative current electrical conduction in Li3PO4 was interpreted through several processes, which can be associated to two different models: the non-overlapping small polaron tunneling (NSPT) model in the region I and the overlapping large polaron tunneling (OLPT) model in the region II. Elliot's theory was used to interpret the conduction mechanism, and all Elliot's parameters were determined.

Structural phase transition, vibrational analysis, ionic conductivity and conduction mechanism studies in an organic-inorganic hybrid crystal: [N(CH3)3H]2CdCl4

Hybrid organic-inorganic metal halides (HOMHs) present good application prospects in optoelectronics and photovoltaic as a result of their richness in physical properties and diverse structural assemblies. Herein, the organic-inorganic hybrid compound, [N(CH3)3H]2CdCl4 (1) is successfully synthesized by slow evaporation at room temperature. X-ray powder diffraction shows that 1 crystallizes in the orthorhombic system with the space group Pna21. The chemical composition of 1 is discussed by a STEM−EDS. Two-phase transitions at T1=253/263 ​K and T2=290/300 ​K are confirmed by the differential scanning calorimetry (DSC) curve. The measurements of the electrical properties are performed in the 10−1−107 ​Hz frequency range and 220−335 ​K temperature interval. The study on the charge transfer mechanism of 1 is done with the help of Elliott’s theory. The conduction mechanism in 1 is interpreted by different approaches: the correlated barrier hopping (CBH) model in phase I, the non-overlapping small polaron tunneling (NSPT) model in phase II, and the overlapping large polaron tunneling (OLPT) model in phase III.

Study of charge transfer mechanism and dielectric relaxation of all-inorganic perovskite CsSnCl3.

In the field of commercialization, lead-free metal halide perovskite materials are becoming more popular these days because of their prospective use in solar cells and also in other optoelectronic applications. In this paper, a non-toxic CsSnCl3 metal halide is successfully synthesized via the slow evaporation solution growth technique. Such systematic characterizations as differential scanning calorimetry (DSC) measurements, dielectric measurements, and variable-temperature structural analyses indicate that CsSnCl3 goes through a reversible phase transformation at T = 391/393 K from the monoclinic to the cubic system. Optical measurements of CsSnCl3 reveal a direct band-gap value of about 3.04 eV. The study of the charge transfer mechanism of CsSnCl3 is carried out based on Elliott's theory. The conduction mechanism in CsSnCl3 is interpreted through the following two approaches: the non-overlapping small polaron tunneling (NSPT) model (monoclinic phase) and the overlapping large polaron tunneling (OLPT) model (cubic phase). Moreover, the high dielectric constant of CsSnCl3 which is associated with a low dielectric loss makes it a possible candidate for energy harvesting devices.

Enhanced electrical conductivity in Zr-Doped (La0.7Ba0.3)(Mn0.5Fe0.5)O3 solid solutions

The perovskite ([Formula: see text][Formula: see text]([Formula: see text][Formula: see text][Formula: see text]O3, where [Formula: see text] = 0.1, 0.2 and 0.3, ceramics were synthesized by solid-state reaction method. The introductory structural studies were followed through by X-ray diffraction technique and the results have disclosed that all the samples were crystallized into an isolated phase. The Zr substitution in the resulting solid solutions increases the electrical conductivity and the maximum value of ac conductivity has been found to be [Formula: see text]118.8 S [Formula: see text] cm[Formula: see text] for [Formula: see text] = 0.3 at 200[Formula: see text]C (at 1 MHz). The frequency dependence of ac conductivity data follows Jonscher’s power law. The variation of the exponent [Formula: see text] versus temperature follows the nonoverlapping small polaron tunneling (NSPT) model. The dielectric relaxation has been observed to be of non-Debye nature for all measuring temperatures (50–200[Formula: see text]C). The impedance spectroscopy reveals that all the samples exhibit negative temperature coefficient of resistance (NTCR) behavior. The prepared samples (for [Formula: see text] &gt; 1) are supposed to be suitable for cathode materials in SOFCs.

Investigation of optical properties and electrical conductivity mechanism of Fe2O3–Sm2O3–ZnO–P2O5 quaternary glass nanocomposite systems

The influence of incorporation of Fe2O3 on the physical, structural, optical, and electrical properties of zinc-samarium phosphate glasses synthesized via conventional melt quenching technique have been studied. The polycrystalline nature, crystallinity percentage, and average size of the developed nanocrystallites in the as-prepared samples have been determined from the obtained X-ray diffraction data. TEM micrographs and SAED patterns confirm the formation of nanocrystallites over the amorphous glassy network. EDX spectra reveal the weight and atomic percentage of each constituent element. Density and molar volume data show inverse relation, which has been explained by the formation of non-bridging oxygens. The optical bandgap energy (Eopt) values, obtained from UV-Vis spectroscopic data, and the calculated Urbach energy (EU) values reduce with increasing Fe2O3 concentration (x). The Fe2O3 concentration (x) dependent refractive index, electronic polarizability, molar refraction, oxide ion polarizability, optical basicity, and electronegativity have been determined. Mott's variable range hopping model is used to explain the DC conduction mechanism, whereas the non-overlapping small polaron tunneling model is used to explain the AC conduction mechanism. Both the AC and DC conductivity are found to increase with the incorporation of Fe2O3. The scaling property of AC conductivity reveals that the conductivity relaxation process depends on the structural composition of the present sample but is independent of temperature.