Overlapping Large Polaron Tunneling Research Articles

Synthesis and study of structural, electric, and dielectric behavior of La0.5Sm0.2Sr0.3Mn1-xFexO3 perovskite

In this study, the synthesized samples La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) were thoroughly investigated for their crystalline structure, electrical conductivity, and dielectric properties, the samples were prepared using autocombustion method. According to the X-ray diffraction study, the samples crystallized in an orthorhombic symmetry with the Pnma space group. To measure the dielectric characteristics, impedance spectroscopy was conducted over the temperature range of 100–260 K and a frequency range of 100 Hz to 1 MHz. Measurements of AC conductivity are indeed utilized to investigate the transport properties of materials being studied. The results indicated that both temperature and frequency significantly influence the conduction process. Three theoretical hypotheses were proposed to explain the hopping conduction: overlapping large polaron tunneling (OLPT), the non-overlapping small polaron tunneling (NSPT) mechanism, and correlated barrier hopping (CBH). It is also shown that the conductivity diminishes with an increase in Fe content. La0.5Sm0.2Sr0.3Mn1-xFexO3 (x = 0.05, 0.15 and 0.20) can be used in electronic applications because of the high permittivity values confirmed by the dielectric measurements. With the aim of evaluating the distinct impacts of electrodes, grain boundaries, and grains on the complex impedance results, an appropriate alternative electrical circuit was utilized. Analysis of the sample's modulus indicated non-Debye characteristics and electrical relaxation phenomena. The materials exhibit good electrical properties, as well as strong chemical and thermal stability.

Optical, AC conductivity and antibacterial activity enhancement of chitosan-silver nanocomposites for optoelectronic and biomedical applications

This study is aimed to prepare and investigate the optical, electrical and antibacterial activity of the environmentally friendly (green) chitosan (Cs)/silver nanocomposites. TEM demonstrated that AgNPs have a spherical shape with particle size ranged from 3 nm to 25 nm. UV analysis spectra of Cs and Cs/Ag nanocomposites showed that, increasing the content of AgNPs led to a noticeable increase in the values of Urbach energy (E U ) and a dramatic decrease in both the indirect (E ig ) and direct (E dg ) optical bandgap energies. It is found that (E ig ) and (E dg ) are decreased from (4.72/5.31 eV) to (2.47/4.19 eV). The formation of the AgNPs is verified by the existence of surface plasmon resonance (SPR) peak at ∼ (421–450) nm. Wemple-DiDomenico and Sellmeier oscillator models are employed and displayed a clear enrichment in the dispersion energy (E d ) and oscillator energy (E 0) as well as the linear and nonlinear optical parameters of Cs. It is observed that the linear (χ(1)) and nonlinear (χ(3) and n2) parameters are enhanced from 0.083, 0.868 × 10−14 and 1.584 × 10−12 to 0.153, 9.762 × 10−14 and 4.088 × 10−12. The novel results in our study nominate Cs/Ag nanocomposites for applications in linear/nonlinear optical devices. AC conductivity behavior of Cs and Cs/Ag nanocomposites is analyzed based on Jonscher’s law and the analysis showed that the overlapping large polaron tunneling (OLPT) is the dominant conduction mechanism for our samples. It is clear that the values of dielectric constant (ε′) of Cs and Cs/Ag nanocomposites are higher confirming the presence of interface polarization (IP) relaxation. Moreover, it is found that the antibacterial activity of Cs against Gram-negative (P. aeruginosa) and Gram-positive (B. thuringiensis) bacteria is found to be enhanced with increasing the content of Ag NPs. These results suggested that Cs/Ag nanocomposites will be good source for preparing bio-nanocomposites for use in many biomedical and industrial applications.

Investigation of thermal, optical properties, AC conductivity and broadband dielectric spectroscopy of poly(ethyl methacrylate)/poly(vinyl chloride) polymer blend

This work reports the structural, thermal, optical and electrical properties of PEMA, PVC and their polyblends. These properties are investigated by FTIR, TGA, UV/Vis and broadband dielectric spectroscopy. FTIR spectra showed that the characteristic bands of PEMA and PVC are affected by blending and displayed red and blue shifts confirming that an intermolecular interaction between PEMA and PVC is occurred. Thermal degradation kinetics of PEMA, PVC and its polyblend samples is investigated in details and the thermal properties of each decomposition stage are estimated. UV measurements analysis revealed that Urbach energy (EU) is increased while optical bandgap decreased upon increasing the PVC content. The indirect and direct band gap (Eig/Edg) values are decreased from (3.95/4.21) to (3.10/3.92) eV. Also, upon increasing the content of PVC, the lattice dielectric constant (εL) is increased from 2.71 to 7.83. Wemple-DiDomenico model is applied for investigating the refractive index dispersion and to calculate the oscillator and dispersion energies. It is observed that the linear/nonlinear parameters are increased nonlinearly with increasing the PVC content. χ(1), χ(3) and n2 values are found to increase from 0.104, 0.213 × 10−13 and 4.01 × 10−12 to 0.363, 31.26 × 10−13 and 5.33 × 10−12. These results make PEMA/PVC polyblend strong candidates for use in the development and design of advanced optoelectronic devices. AC conductivity (σac) and dielectric measurements are carried out at various temperatures in wide frequency range. Jonscher power law is applied and showed that the predominant conduction mechanism in our samples is overlapping large-polaron tunneling (OLPT). The dielectric constant and electrical impedance are found to be frequency and temperature dependent. The investigation of the electric modulus (M*) revealed that M′ is increased non-linearly with increasing the frequency, while M″ spectra displayed two different modes of relaxation. The interfacial polarization (IP) is observed in low frequency region, while, dipolar relaxation is detected in high frequency region.

Polaron-mediated transport and relaxation phenomena in the lead zinc niobate (PZN) modified bismuth ferrite solid solution

To investigate the dielectric and conductivity properties of PZN modified BF solid solution high temperature mixed oxide technique is employed. The material is subjected to analysis using XRD, SEM, and impedance spectroscopy. A polycrystalline PZN-BF sample with an average crystallite size of 63.3 nm has been formed. The scanning electron micrographs show that the grains and grain boundaries are distributed suitably. dielectric characteristics of the 0.1PZN-0.9BF compound are studied at frequencies ranging from 1 kHz to 1 MHz and temperatures ranging from ambient temperature to 400 °C. The confined mobility of charge carriers causes nearly continuous loss (NCL) behavior at low temperatures (<200 °C). High-temperature relaxation resulting from charge carrier hopping induces maximum loss and elevated conductivity. Rendering to the Overlapping Large Polaron Tunnelling (OLPT) model of conductivity, the transport mechanism in this modified BiFeO3 (BF) compound is facilitated by the short-range hopping of polarons. The NTCR behavior from Arrhenius plot of ac conductivity and temperature independent conductivity relaxation from loss modulus (M'') analysis are demonstrated. Sensors, actuators, and optoelectronic devices can benefit from the PZN-modified BF compound's electrical and dielectric characteristics, which have been studied in detail.

Dielectric and Electrical Behavior of Apraseodymium Based Tungsten Bronze Ceramics

AbstractThe ceramic oxide Na2Ba2Pr2W2Ti4Nb4O30 (NBPWTN) is prepared by a mechanical mixed oxide route. The compound formation and the phase are concluded from the x‐ray diffraction pattern taken at room temperature (XRD). The uniform distribution of grains of various sizes with negligible voids is studied from scanning electron micrograph of the sample pellet. The presence of dielectric dispersion and ferroelectric phase in the material is observed from the temperature‐dependent dielectric parameters at selected frequencies. The existence of ferroelectricity in the material is further confirmed by the room temperature hysteresis loop. Impedance spectroscopic studies informed about the correlation between the microstructure and electrical behavior. The frequency variation of AC conductivity refers to Jonscher's law. The temperature variation of frequency exponent term n indicates OLPT (overlapping large polaron‐tunneling) model of the conduction mechanism in the sample. NBPWTN is a strong candidate for applications involving thermistor‐related devices because of the temperature dependency of resistance. The value of temperature sensitivity coefficient β in our investigation is achieved between 2000 and 11 000 K, confirming that the material has a high‐temperature stability property and is ideal for high‐temperature electronics applications. The high room temperature dielectric constant value of the ceramic (around 500) is useful for dielectric capacitor applications.

Dy3+ and Sm3+ ratio variation effects on electrical properties of lithium fluoride bismuth borate glass system

Since less attention was paid to study of electric properties of glasses doped with RE ions, in present work conductivity (AC and DC) and dielectric properties of Dysprosium (Dy3+) and Samarium (Sm3+) ion co-doped 60B2O3•30LiF•10Bi2O3 glasses were examined. Conventional melt quench method was used to synthesize the amorphous glass samples. It was observed that dc conductivity obeyed the Arrhenius law and the ac conductivity followed Jonscher's Power Law. The Conductivity mechanism was investigated on the basis of the trend followed by frequency exponent “s” parameter and all the compositions satisfied the Overlapping large polaron tunnelling (OLPT) model. Dielectric properties: Dielectric Constant (ε′), Dielectric loss (ε'′) and tangent loss (tanδ) were also investigated and observed to decrease with frequency and finally attained a minimum constant value at higher frequencies. The high rate of change in dielectric properties at low frequencies was attributed to space charge polarization while at higher frequencies it was decreased due to inertia of ions. Cole-Cole plots encompasses depressed semicircular arcs which evidenced the presence of constant phase element and non-Debye relaxation behaviour.

An investigation of structural, thermal, and electrical conductivity properties for understanding transport mechanisms of CuWO4 and α-CuMoO4 compounds.

Recently, inorganic oxide components with high ionic conductivity have been widely explored due to their high stability, safety, and energy density properties. In this context, the present work focuses on the inorganic oxides CuMO4 (M = W, Mo), which have been successfully synthesized using the traditional solid-state method. They were characterized by X-ray powder diffraction, thermal analysis, and complex impedance spectroscopy. X-ray diffraction data refined via the Rietveld method indicated that these compounds are well crystallized in the triclinic system with the P1̄ space group. Besides, the electrical conductivity behavior of these materials was analyzed using the impedance spectroscopy technique in the frequency range of 100 to 106 Hz and in the temperature range of 443 K to 563 K. The absence of a phase transition observed in the calorimetric study was confirmed by the σg and ωh variations as a function of temperature. The AC conductivity was analyzed by Jonscher's power law. The outcomes of the study on charge transportation in CuMO4 (where M = W, Mo) suggest that the overlapping large polaron tunneling (OLPT) mechanism was present in CuMoO4, while the correlated barrier hopping (CBH) and the non-overlapping small polaron tunneling (NSPT) were present in CuWO4. A correlation between the crystal structure and the ionic conductivity was established and discussed. For the two title compounds, modulus analysis revealed that the charge carriers were mobile over short and long distances at low and high frequencies, respectively. The temperature variation of the M'' peak showed a thermally activated relaxation process.

Dielectric behavior and impedance spectroscopy of Niobium substituted Lanthanum based orthovanadates at high temperatures

We present the detailed study of the temperature dependent dielectric properties, impedance spectroscopy and electrical conductivity of LaV1−xNbxO4 (x=0–1) samples prepared by the solid-state reaction method. The dielectric constant (ϵr′) increases (decreases) with increase in the temperature (frequency); while, the magnitude of ϵr′ remains almost invariant (order of 104 at 100 Hz and 600 °C) with x. The single phase x=0 (monoclinic-monazite, P21/n) and x=1 (monoclinic fergusonite, I2/a) samples show the lower values of loss factor [tanδ= (4–8)] as compared to the x=0–0.8 samples [tanδ= (12–18)] having mixed tetragonal and monoclinic phases, which indicates the strong correlation between the crystal structure and the dielectric properties. The real part of impedance (Z′) decreases with both temperature and frequency, and the observed weak relaxation remains almost unaltered with x. The imaginary part of impedance (Z′′) shows strong relaxation peaks shifting towards higher temperatures with frequency, which is attributed to the effect of grains, grain boundaries, and electrodes in the samples. The activation energy of the relaxation process is estimated to be 0.8–1.0 eV for the x=0–0.6 samples, and ≈1.4 eV for the x=0.8; whereas the x=1 sample shows two values (≈0.5 eV and ≈1.0 eV) in the higher and lower temperature range, respectively. Further, the change in total conductivity with the angular frequency, which found to be in the range of 10−3 to 10−5 S/m, is fitted using the Jonsher power law. The analysis suggests the overlapping large polaron tunneling (OLPT) model for all the samples, whereas the x = 1 sample exhibit a transition near 480 °C and at higher temperatures it shows non-overlapping small polaron tunneling (NSPT) and quantum mechanical tunneling (QMT). This transition is corroborated by the tangent loss curves and may be associated with the change in structure.

Effects of Ce3+ doping on magnetic and dielectric properties of cobalt zinc manganese ferrites for high frequency applications

In this paper, a constant quantity of Co2+ ions and a series of Ce3+ ions were used to substitute Fe3+ ions to control the magnetic and electrical properties of the pristine Zn–Mn nanoferrites with the formula Co0.5Zn0.25Mn0.25CexFe2-xO4 (CZMC). The addition of a suitable content of Ce3+ ions (x = 0.1) enhanced the magnetization (with an enhancing ratio of 9.43 %), initial permeability (with an enhancing ratio of 31.06 %), and coercivity (with a decreasing ratio of 12.86 %). The CZMC nanoferrites can operate from 13.5 GHz to 16.5 GHz, which can be utilized in high frequency-based technical purposes such as magnetic memories, filters, and transformer cores. The AC conductivity results of the CZMC nanoferrites are in correspondence with Jonscher's single-power law, and the conduction mechanism is established to be attributed to the overlapping large-polaron tunneling model. Nyquist plots of the samples revealed that the diameters of the semicircles decrease as the temperature increases, confirming the semiconducting behavior with one semicircle due to the electrode and grain boundary contributions to the conduction process. The high-frequency response of the CZMC nanoferrites revealed that they could operate in the frequency range of 13.5 GHz–16.5 GHz, which is suitable for electronic and microwave devices. The dielectric loss value reduces with Ce replacement (with a decreasing ratio of 66 %), suggesting it might be a candidate for planar inductor and transformer cores at high-frequency applications.

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.

Studies of structural, dielectric, conductivity, leakage current mechanism, and efficiency of complex electroceramic

Bismuth ferrites are quite interesting because of their high conductivity and dielectric constant. Recent times now need innovative materials with high mechanical strength, minimal energy loss, and cost effective. The analysis of X-ray diffraction pattern/data and scanning electron micrograph provides the formation of complex bismuth ferrite containing lithium and tungsten of a composition Bi1/2Li1/2Fe1/2W1/2O3, with monoclinic symmetry. The relation between the electrical and dielectric characteristics was examined in the frequency region from 1 kHz to 1 MHz at different temperatures (25–500 °C). The electrical conductivity experiments on the compound containing lithium and tungstate produced some exciting findings. As the frequency increases, the ac resistivity showing decreasing trend with small resistance and large conductivity. With the help of non-overlapping small polaron tunneling (NSPT) and overlapping large polaron tunneling (OLPT) models, temperature-frequency dependent conduction mechanisms have been explained. When electrical characteristics are examined using impedance spectroscopy (non-Debye relaxation), the contributions of grain and grain boundaries effect in the material are observed in the material. The Ohmic and Space Charge Limited Current conduction mechanism (SCLC) were found at low and high electric field (voltage) under forward bias current-voltage situations. The energy storage efficiency of the material is 61.80 %, obtained at room temperature with an applied electric field (−3 to +3 kV/cm) at a frequency of 50 kHz from the hysteresis loop. It implies that the material is promising for pulsed power energy storage capacitors.

Charge transport mechanism, dielectric relaxations and relaxor ferroelectric properties of Sm2MgMnO6 double perovskite

This study investigates the charge transport mechanism, dielectric relaxation and relaxor ferroelectric properties of Sm2MgMnO6 which exhibits monoclinic crystal structure with space group P21/n. The charge carriers conduction mechanism in the temperature range 150 K–239 K and 244 K–304 K are correlated barrier hopping (CBH) and overlapping large polaron tunneling (OLPT), respectively. The maximum barrier height associated to CBH model is 0.26 meV. The dc activation energy associated to CBH and OLPT model are 0.11 eV and 0.91 eV respectively. The polaron hopping energy associated to Mott's variable range hopping model is 0.11 eV at 244 K. The value of tanδ varies from 0.004 to 3.329 in temperature range 151.07 K–306.87 K and frequency range 1 kHz–800 kHz. The temperature variation of ε′, ε″ and tanδ shows a single relaxation which follows Vogel–Fulcher (VF) law. The VF law and the shape of P–E hysteresis loop confirms the relaxor ferroelectric nature of the studied material. The saturated polarization (PMax), remnant polarization (Pr) and coercive field (Ec) depend on both the electric field (E0) and frequency (f). The loop area (A′) and dielectric breakdown field (EBD) depend on E0 as A′∝E02 and EBD∝E0, respectively. The PMax, Pr and Ec depend on f as PMax∝f−0.13, Pr∝f−0.48 and Ec∝f−0.48, respectively. The energy storage efficiency (η) varies with frequency as: η%=20.44f0.21.

Structural, electrical and dielectric properties of ZnFe2O4/Cu2S 3D heterostructures

This work reports the fabrication of zinc ferrite-copper sulphide (ZnFe2O4/Cu2S) 3D heterostructures and subsequent investigation of the spectroscopic behaviour of various electrical parameters like conductivity, impedance and dielectric loss. The study reveals a non-monotonic behaviour of the real component of impedance (Z’), while the imaginary component of impedance (Z’) exhibits a temperature-dependent relaxation frequency, with an estimated activation energy (E a ) of 220.13 meV. The dc conductivity (σ dc ) measurements reveal the semiconducting nature of the sample and a transition from a ferrimagnetic to a paramagnetic behaviour is reported at the Curie temperature of 327 K. In case of ac conductivity (σ ac ), Jonscher’s power law σ ac = Aω n is followed and the exponent n is found to lie in the range 0.679–0.735 at different temperatures, which is best fitted into a polynomial of degree six. The temperature variation of n is suggestive of the overlapping large polaron tunnelling (OLPT) model. Further, ac activation energy (E ac ) is also calculated, which is found to be smaller than the dc activation energy (E dc ), indicating electron hopping between Fe3+ and Fe2+ ions. The numerically computed staying time (τ) of electrons in Fe3+/Fe2+ ionic sites varies with frequency as well as with temperature, ranging from 10−6s to 10−19s. A significant decrease in dielectric loss (tanδ) to the tune of 99% (from 75 at ∼100 Hz to 0.89 at ∼1 MHz) is reported at room temperature. In the present scenario, when smart materials like spinel ferrites have garnered significant attention for their promising magnetic and electric properties, our studies of the ZnFe2O4/Cu2S 3D heterostructures may provide immense possibilities for tailored applications in various electromagnetic applications.

Effect of Sr doping on electronic transport properties of SnS2 hexagonal nanoplates

In this work, the electronic transport properties of SrxSn1-xS2 (x = 0, 0.02, 0.04, 0.06 and 0.08) nanoplates synthesized by hydrothermal method have been reported. AC conductivity, electric modulus and impedance spectra nanoplates have been studied in frequency and temperature ranging from 1Hz to 1 MHz and 313K–453K, respectively. AC conductivity data of the SrxSn1-xS2 nanoplates obeys the Almond-West relationship. In SrxSn1-xS2 nanoplates conduction governs by overlapping large-polaron tunnelling (OLPT), quantum mechanical tunnelling (QMT) and small polaron quantum mechanical tunnelling (SPQMT) mechanisms for x = 0, x = 0.02 and x = 0.04, 0.06 and 0.08, respectively. A modified KWW model has been used to understand the electric modulus behaviour of SrxSn1-xS2 nanoplates. The observed scaling behaviour of the imaginary component of the electric modulus supports the assertion of frequency exponent (s) with temperature about the conduction mechanism. The Nyquist plots are well-fitted with a double R-CPE model. The activation energy values estimated from conductivity (0.68–0.73 eV) and electric modulus (0.69–0.72 eV) analysis are in coherence.

Temperature and frequency-dependent electrical transport studies of manganese-doped zinc ferrite nanoparticles

Manganese substituted zinc ferrite nanoparticles (Zn1-xMnxFe2O4, x ≤ 10%) have been successfully synthesized by the co-precipitation technique. The x-ray diffraction technique was employed to determine the structure of nano-ferrites at room temperature. SEM, EDX, and FT-IR spectroscopy were used to establish surface morphologies, elemental composition, and phase formation. Impedance spectral analysis was carried out at various temperature ranges varying from 600 K to 870 K in the frequency range of 100 Hz to 2 MHz. The dielectric parameter measurements were used to compute the types of conduction in the synthesized samples. The significance of the distribution of cations between A and B sites was analyzed using frequency and temperature-dependent ac electrical transport studies of the synthesized nanoparticles. The conduction mechanism, overlapping large polaron tunneling (OLPT) was found in Zn1-xMnxFe2O4 nano-ferrite system.

Consistency between theoretical conduction models and experimental conductivity measurements of strontium-doped lanthanum manganite

La0.9Sr0.1MnO3 nanoparticles are elaborated using the citrate-gel route. The X-ray patterns show that the prepared sample crystallizes in the rhombohedral symmetry. Interesting results were obtained from the electrical conductivity measurements of the lanthanum manganite doped low strontium content. Indeed, numerous conduction models are used to analyze the electrical conductivity response. It is found that transport properties are governed by hopping processes at different temperature ranges. Such mechanisms explain the evolution of the DC-conductivity as well as the displacement of charge-carriers with temperature excitation. Then, thermal activation of the charge-carriers is confirmed. The temperature dependence of the frequency exponents reveals the contribution of Non-overlapping Small Polaron Tunneling (NSPT), Quantum Mechanical Tunneling (QMT), Over-lapping Large Polaron Tunneling (OLPT) and Correlated Barrier Hopping (CBH) to the transport properties. Conductivity spectrum shows a significant increase with frequency in the temperature range [80–500 K]. The frequency dependence of the AC-conductivity obeys to the "Double Jonscher Power Law" in the temperature range [80–300 K]. From 340 to 500 K, it is governed by the "Single Jonscher Power Law". Moreover, a high frequency plateau is observed presenting a percolation behavior in the conductivity spectrum. The deduced values of the disorder and hopping energies show the impact of hopping distance and polaron radius on the charge-carriers transport.

Microstructural analysis, magnetic interactions, and electrical transport studies of [formula omitted] nanoparticles

This study focuses on the synthesis, structural characterization, magnetic interactions, and electrical transport properties of copper-doped zinc ferrite (Zn1−xCuxFe2O4) nanoparticles with varying Cu concentrations (x = 0.00, 0.03, 0.06, 0.10) using the co-precipitation method. The structural and morphological properties were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), through TEM, while the BET technique was employed to determine the surface area, pore size, and specific surface area. The synthesized nanoparticles were found to exhibit a cubic spinel structure with lattice parameters decreasing as Cu content increased. The photoluminescence spectra indicated emission energies and wavelengths in the green region of the visible spectrum. The magnetic properties were studied using a vibrating sample magnetometer (VSM), revealing that Cu+2 doping resulted in the highest saturation magnetization (16.47 emu/g) by using an applied up to 50 kOe. The electrical properties were studied in the frequency range from 25 Hz to 2 MHz as a function of temperature ranging from 300 K to 480 K with an increment of 20 K. The electrical conductivity of the nanoparticles was found to increase with temperature and Cu content which is attributed to the thermally activated mechanism and predominantly dominated by overlapping large polaron tunneling (OLPT). The activation energy obtained from DC conductivities decreased order 0.63–0.48 eV for the synthesized nanoparticles. The temperature-dependent drift mobility exhibited p-type semiconducting behavior. Overall, the results suggest that Zn1−xCuxFe2O4 NPs have the potential for use in various applications, including sensors, energy storage, and catalysis.

Structural, dielectric, magnetic and magnetoelectric studies of (1-x) BaFe12O19-x BiFeO3 composites

The synthesis of multiferroic (1-x) BaFe12O19-x BiFeO3; (x = 0.05, 0.08, 0.10) composites was carried out with solid state reaction. The XRD data confirmed the formation of the composites with phases of both compounds. The low values of Rietveld refinement parameters along with modified lattice parameters of both hexaferrite and multiferroic phase reconfirmed the amalgamation of phases. FESEM with EDX were utilized for morphological study and elemental compositional analysis in the composites. The dielectric constant and tanδ both parameters showed typical low frequency dispersion. A mild anomaly in dielectric constant and tangent loss is quite noticeable near to magnetic transition temperature (TN) of BiFeO3 suggests the possible occurrence of magnetoelectric effect in prepared composite system. The fitting of AC conductivity data suggested the OLPT (overlapping large polaron tunneling) conduction process in the composite system. The saturation magnetization (Ms) showed a decreasing trend with increment of BiFeO3 content in composites owing to substituted Fe3+ ion in spin-up state. Coercivity (Hc) found in good agreement with magnetocrystalline anisotropy of hexaferrite phase. The improvements in magnetoelectric coupling coefficient of barium hexaferrite were clearly noticeable with the introduction of BiFeO3 phase owing to piezoelectric coefficient and magnetostriction of ferroelectric and ferrite phases respectively.

Insight into OLPT model conduction mechanism and dielectric relaxation of lead borate glass containing Cr and Ge ions

Lead borate glass with compositions 25B2O3–73.8PbO–xGeO2-(1.2 − x) Cr2O3 (x ≤ 1.2 mol. %) is fabricated by the melt quenching procedure. The electrical conductivities (σdc, σac) of fresh samples are measured in the frequency range 100 Hz–1.0 MHz and temperature range 303–393 K. The anomalous behavior observed in the dc activation energy at x = 0.6 mol% is argued to the formation of bridging and non-bridging oxygen bonds. These bonds are formed due to substitution of GeO2 to the expense of Cr2O3 ions in the PbO–B2O3 network. The dependence of ac conductivity on frequency is analyzed through the power law: σacαωs where s ≤ 1.0. The experimental results of s for the considered samples have shown that overlapping large polaron tunneling (OLPT) is the possible conduction model in the considered frequency and temperature ranges. The strength of the OLPT model established on the normal Mayer–Neldel (MN) rule is analyzed and discussed. Furthermore, results of the real and imaginary dielectric constant composed with Cole–Cole diagrams for investigated samples are presented and discussed.

Structural evolution, dielectric relaxation, and charge transport characteristics of formamidinium lead iodide (FAPbI3) perovskite

Recently, hybrid halide perovskite solar cells have drawn the researchers’ attention, owing to their high-power conversion efficiency. Among the different compounds, MAPbI3 (MA = Methylammonium CH3NH3) and FAPbI3 (FA = Formamidinium CH(NH2)2) are especially potential candidates since their bandgap suited the energy range of visible light. Here, the hybrid perovskite FAPbI3 is successfully synthesized via the inverse temperature crystallization method. Different characterization techniques such as variable-temperature structural analyses, differential scanning calorimetry (DSC), and impedance spectroscopic analysis show that FAPbI3 presents a phase transition at T = 300 K from the hexagonal to the cubic symmetry. Optical analysis of FAPbI3 shows the direct band-gap value of ∼1.4 eV. FAPbI3 is characterized by impedance spectroscopy technique performed in the 10−1–106 Hz frequency and 210–390 K temperature ranges. The alternating current (AC) conductivity is illustrated in terms of Jonncher's power law. The study on charge transportation within FAPbI3 suggests the presence of the NSPT (non-overlapping small polaron tunneling) and OLPT (overlapping large polaron tunneling) models in the hexagonal and cubic phases, respectively.