Dependent Conductivity Studies Research Articles

Unravelling the crossover amongst band and various hopping conduction mechanisms in Mo doped ZnO thin films owing to carrier localization at defects

Understanding the carrier transport mechanism of transparent conducting oxides is crucial for its application in optoelectronic devices. Although, electrical transport mechanisms of various trivalent cation doped ZnO films have been reported adequately, a substantial study is needed to understand the transport mechanism in ZnO doped with higher valence (>+3) dopants. Unlike Al, In and Ga doped ZnO where metal-insulator transition is commonly observed, in this study, the crossover amongst band and various hopping mechanisms has been observed in the temperature range of 300–10 K in Mo doped ZnO films deposited at various substrate temperatures. All the films show electrons as the majority charge carriers and notably, the film deposited at 573 K shows the highest conductivity value of 167.22 (Ω.cm)−1. In-depth analyses of the conduction mechanism reveal grain boundary scattering dominated band conduction at and not far below the room temperature, which is shifted towards nearest neighbor hopping (NNH), and then to Mott variable range hopping (VRH) type of conductions as the temperature is decreased further. Unfamiliarly, a modified Efros-Shklovskii (ES) VRH type of conduction mechanism is shown to prevail in the lowest measured temperature range (∼30–10 K). Unprecedentedly, it is demonstrated here that the activation energies for various conduction mechanisms are higher at lower vacuum condition (∼10−1 mbar) as compared to those measured at higher vacuum condition (∼10−3 mbar) implying an added role of the surface traps in the charge transport process. The temperature dependent conductivity and X-ray photoelectron spectroscopy (XPS) studies proclaim that the film deposited at 573 K possess fewer defects related disorder for carrier localization as compared to the films deposited at 523 K and 698 K.

Temperature dependent conductivity studies of KNN modified NBT-ST ternary systems

Temperature- and frequency-dependent electrical transport mechanism of a lead-free 0.72Na0.5Bi0.5TiO3-0.2SrTiO3-0.08K0.5Na0.5NbO3 ceramic is investigated using complex impedance spectroscopy (CIS) in a wide temperature range 50 °C to 650 °C. The ac and dc conductivity variation analysis were carried out as a function of frequency f and temperature (T) using certain empirical models. Jonscher power law is well fitted to the frequency varying conductivity data and the relatively higher value of S-parameters are obtained around Tm (at which dielectric value attains its maximum value) indicating the presence of a short-ranged relaxation process. Considering Jump relaxation model (JRM), the values of activation energies calculated from log σdc and log fH vs 1000/T curves indicate that the unproductive hops of charge transporters number increase with rise in temperature. The scaling behavior of the conductivity data provides evidence in the favor of the thermally induced relaxation process. Short ranged relaxation is analyzed more extensively using modified KWW function from complex modulus plots. Additional evidence in favour of the thermally induced relaxation process is provided using the scaling characteristics of the conductivity and modulus values.

Synthesis and ion transport property studies of a new K+ ion conducting nanocomposite polymer electrolytes

Synthesis and ion transport property studies of a new K+ ion conducting nanocomposite polymer electrolytes (NCPEs): (1 − x) (70PEO:30KCl) + x TiO2 where 0 ≤ x ≤ 20 wt%, are reported. The present NCPEs films have been synthesized using a recently developed hot-press method. The maximum ionic conductivity (σ ∼ 5.3 × 10−5 S·cm−1) have been obtained at the composition: [95(70PEO:30KCl) + 5 TiO2] and this has been referred to as optimum conducting composition (OCC). Materials characterization have been done with the help of scanning electron micrograph (SEM), thermo-gravimetric analysis (TGA) and differential scanning calorimetric (DSC) studies. Ion transport properties have been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n) and ionic transference number (tion). To compute the activation energy (Ea) values of different samples, temperature dependent ionic conductivity studies have been done.

Conduction mechanism in excess Bismuth doped Strontium Bismuth Niobate ceramics

Strontium Bismuth Niobate ceramics with excess Bismuth doping (0%wt – 20%wt) were prepared using solid state reaction method. X-ray diffraction studies reveal the decrease in c-axis orientation as bismuth content increases up to 5 ​wt%, beyond that it increases. The dielectric studies were carried out at room temperature as well as at higher temperatures. The ferroelectric properties were found to improve with excess bismuth doping to some extent (5%), indicating compensation for bismuth losses during heat treatment. Temperature dependent dc conductivity studies were done and attempts were made to explain extrinsic and intrinsic conduction mechanisms in Strontium Bismuth Niobate. In low temperature region, the activation energy was found to be very low (0.08eV–0.16eV), which increases (1.07eV–1.14eV) due to introduction of intrinsic defects. A detailed conduction mechanism is presented with excess bismuth doping in Strontium Bismuth Niobate.

Ion transport property studies of a new TiO2 dispersed Na+ ion conducting nanocomposite polymer electrolytes

Ion transport property studies of a new Na+ ion conducting nanocomposite polymer electrolytes (NCPEs): (1-x) [75PEO:25NaPO3] + x TiO2 where 0 ≤ x ≤ 18 wt%, are reported. The present NCPEs films have been casted using a recently developed hot-press method. The maximum ionic conductivity (σ ∼ 2.3 × 10-5 S.cm−1) have been obtained at the composition: [95(75PEO:25NaPO3) + 5 TiO2] and this has been referred to as optimum conducting composition (OCC). Ion transport properties have been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n) and ionic transference number (tion). To compute the activation energy (Ea) values of different samples, temperature dependent ionic conductivity studies have been done. Solid state polymer battery was fabricated using the NCPE OCC as an electrolyte and studied their cell performances.

Effect of Eu3+ ions on electrical and dielectric properties of barium hexaferrites prepared by solution combustion method

This paper reports the electrical conduction behaviour of Eu3+ substituted barium hexaferrites (BaM) prepared via solution combustion method. The structural analysis confirms formation of hexagonal phase of the prepared samples with a space group p63/mmc (No. 194). The SEM micrographs show that the prepared sample has hexagonal plate like structure. Dielectric constant, dielectric loss and AC conductivity of the prepared samples were calculated over a wide frequency range from 102 Hz to 105 Hz at different temperatures. The temperature dependent dielectric studies were also performed over a temperature range of 30°C–200°C. The non –Debye dielectric nature of the prepared samples and presence of electrical relaxation phenomenon were confirmed from the complex impedance spectroscopy. Electrical modulus analysis confirms that there is negligible electrode effect in prepared the samples. From the frequency dependent AC conductivity studies, we find that the AC conductivity values are constant in the lower frequency region and shift towards the higher value in the higher frequency region, which indicates that the prepared samples follow the Almond-West power law. The AC conductivity values decrease gradually with increase in the concentration of Eu3+ ions increases. The dielectric studies show that by doping of Eu3+ ions, the dielectric constant increases. So the prepared materials can be applicable for microwave devices applications.

Lithium-antimony co-doping induced morphology transition in spray deposited SnO2 thin films

Un-doped, Sb doped (ATO) and Li-Sb co-doped SnO2 (LATO) transparent conducting thin film electrodes have been deposited using facile spray pyrolysis method. X-ray diffraction study is carried out to confirm the crystal structure, phase purity, and textured growth of the films. Surface morphological transition from dendritic to cuboid shape is observed upon Li-Sb co-doping into the SnO2 system from the scanning microscopy measurements. The AFM analysis confirms that as Li doping concentration (1, 3, 5 wt.%) increases, the surface roughness of the films decreases. The UV-Vis transmittance spectra of the SnO2 film doped with 5 wt.% Li and 5 wt.% Sb (LATO5) shows maximum average transmittance of 87.9 % at 550 nm and the calculated direct band gap value is 4.06 eV. The LATO5 film exhibits high carrier concentration and high mobility of 7.54 × 1020 cm−3 and 7.221 cm2/Vs, respectively, due to co-dopant effect at the Sn sites of SnO2 lattice, resulting in enhanced electrical transport properties compared to un-doped SnO2 film. The LATO5 film also exhibits lowest sheet resistance of 32.38 Ω/□ and resistivity of 1.57 × 10−3 Ω cm. The temperature dependent electrical conductivity study is performed to understand the conduction mechanism of the film via estimation of activation energy from Arrhenius plots. The obtained results indicate that the Li-Sb co-doped SnO2 films are potential candidates for alternative transparent conducting electrode system.

Ion conduction and solid state battery fabrication of a new K+ ion conducting nanocomposite polymer electrolytes

Ion conduction and solid state polymer battery studies of a new K+ ion conducting nanocomposite polymer electrolytes (NCPEs): (1 − x) [80PEO:20KI] + x TiO2 where 0 ≤ x ≤ 20 wt%, are reported. NCPEs were cast using a recently developed hot-press method in place of traditional solution-cast technique. The ion conduction phenomenon have been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n) values and various theoretical models. The ionic transference number (tion) of optimum conducting composition of NCPE was also determined with the help of Transient Ionic Current (TIC) technique. The temperature dependent conductivity studies of NCPE OCC have been done and activation energy (Ea) value was determined by using log σ − 1/T Arrhenius plot. Solid state polymer battery was fabricated using the NCPE OCC as an electrolyte and studied their cell performances.

Synthesis and ion conduction mechanism of a new sodium ion conducting solid polymer electrolytes

Synthesis and ion conduction studies of a new Na+ ion conducting Solid Polymer Electrolytes (SPEs): (1-x) PEO: x NaCl, where 0 ≤ x ≤ 50 wt% have been reported. SPE films have been casted by a novel hot- press/dry technique in place of traditional solution cast method. The conductivity measurements as a function of salt complexation revealed SPE film: [70PEO:30NaCl] as the Optimum Conducting Composition (OCC) with σ ∼ 4.5 × 10-6 S/cm at 27 °C. A conductivity enhancement of approximately three orders of magnitude from that of pure polymeric host has been resulted in SPE OCC due to salt complexation in PEO. Ion conduction mechanism have been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion) and various theoretical models proposed for polymeric electrolyte materials. The temperature dependent conductivity studies have also been done to compute the activation energy (Ea) values from ‘log σ-1/T’ Arrhenius plots.

Role of Multiferroic Filler on the AC Response of Bi1‐xBaxFeO3 doped PVA:NH4CH3COO Nanocomposite Gel Polymer Electrolytes

AbstractThe frequency dependent AC conductivity and dielectric studies of multiferroic filler (Bi1‐xBaxFeO3) doped nanocomposite gel polymer electrolyte (NCGPEs) based on PVA:(NH4CH3COO) are investigated in the present work. The nano composite gel polymer electrolyte systems are synthesized for various filler concentrations by solution cast method. The effect of filler concentration on ionic conductivity is studied using AC impedance technique in the frequency range 1–106 Hz. X‐ray diffraction studies reveal the formation of nanocomposite gel polymer electrolyte. The low frequency dispersion in the dielectric response of electrolytes shows the relaxation contribution is superimposed with electrode polarization effects. The relaxation peaks in the NCGPEs are found to shift toward higher frequency side with increasing filler concentration and are suitably correlated to change in morphology of the gel electrolyte system. The variation of AC conductivity with frequency is seen to obey Jonscher's universal power law with the exception of small deviation in the low frequency regime. Modulus formalism of dielectric response suggests that the ion transport is strongly coupled to the polymer segmental motion.

Highly efficient dark to transparent electrochromic electrode with charge storing ability based on polyaniline and functionalized nickel oxide composite linked through a binding agent

Here in this work, a black to transparent efficient electrochromic electrode based on nickel oxide (NiO) functionalized polyaniline (PANI) composite has been prepared. To ensure strong interaction among NiO and PANI, NiO nanoparticles were first functionalized with (3-Aminopropyl) trimethoxysilane (3-APTS) followed by subsequent attachment to monomer. This linking agent 3-APTS makes a bridge between NiO and PANI. Prepared PANI-fNiO composite exhibits extended contrast throughout the visible spectrum as well as in near-IR and near-UV regions with superior coloration efficiency of 138 cm2C-1. The composite PANI-fNiO was found to have improved cyclic stability of 7000 cycles. Thus with such kind of attachment both components synergistically favor each other’s coloration and bleaching, rendering dark (almost) black to transparent electrochromism. Observed hexagonal nanoparticles with ion diffusion channels were observed to give a fast response of 1.5s/2s for coloration and bleaching respectively. Moreover, PANI-fNiO shows pseudocapacitive behaviour with a large areal capacitance of 1.1 F cm−2. Both electronic and ionic charge transport mechanisms in such bonded PANI-fNiO composite have been studied using temperature dependent dc conductivity studies, cyclic voltammetery and electrochemical impedance spectroscopy. The observed results present the strong potential of PANI-fNiO composite as an integrated electrochromic electrode with charge storing ability.

Characterization and Temperature dependent DC conductivity study of bio templated nickel oxide nanoparticles (NiO) and their composites using polyaniline (PANI)

Nickel oxide (NiO) nanoparticles with an average dimension of 28 nm were prepared via the Sol-Gel method using rice starch as bio template at 500 °C for 3h. The DC conductivity of pure NiO nanoparticles measured 1.015 х 10−4 S/cm−1 at room temperature, limiting its wider use in electrical applications. Hence the conductivity of pure NiO was modified by doping polyaniline (PANI). Polyvinyl pyrrolidone (PVP) stabilized polyaniline was synthesized by the oxidative polymerization of aniline using ammonium persulfate and hydrochloric acid as a dopant. The synthesized NiO-PANI composites were subjected to temperature dependent DC conductivity study in the range of 30–150 °C and maximum conductivity 2.1129 х 10−2 S/cm−1 was obtained at 90 °C.

Evidence for dielectric suppression in non-magnetic modified multiferroic bismuth ferrite

Structural, magnetic, and electrical properties of polycrystalline Y-Sc codoped BiFeO3 (BFO) ceramics are investigated. Rietveld refinement and Raman spectroscopy analysis provide strong evidence of structural distortion without changing the structure of parent compound (rhombohedral: R3c) after codoping. Distortion due to nonmagnetic codoping marks an abrupt change in magnetic and electrical properties of BiFeO3. Ferromagnetic property is enhanced with a maximum remanent magnetization of 0.0045 emu/g at higher Sc-concentrations. Codoping improves the ferroelectric properties [Pr=13μC/cm2 at (Y,Sc)=(0.03,0.05)] due to the suppression of oxygen vacancies. The frequency-dependent dielectric properties at various temperatures are investigated. The relaxation peak shifts toward room temperature for Bi1−xYxFe1−yScyO3 ceramics, which eventually appeared above 100°C for parent BFO. The suppression of relaxation peak indicates the change in conduction mechanism for codoped ceramics. The conduction process and the relaxation mechanism in parent and Y-Sc codoped BiFeO3 are investigated with electrical modulus and impedance spectroscopy. Frequency-dependent ac conductivity at various temperatures indicates that the conduction mechanism follows the correlated barrier hopping model and is thermally activated. Temperature dependent conductivity studies at different frequencies reveal that the relaxation process in codoped ceramics is due to the long-range oxygen vacancy movement and the low loss values.

Effect of Mixed Ions and Ion Irradiation on Ionic Conductivity of Solid Polymer Electrolytes

It is a well known fact that conductivity in case of solid polymer electrolytes (SPEs) is due to hopping of ions assisted by the segmental motion of polymer chains. It is observed that the ionic conductivity in SPEs increases with increase in the concentration of ions. After certain critical concentration the conductivity starts decreasing due to the formation of ion pairs. In this work, an attempt is made to identify the concentration at which ion pair formation occurs and hence improve conductivity by incorporating two different ions (salts) in the polymer matrix. SPEs with mixed conducting species PEOxLiBryNaBr with different concentration of salts have been prepared and investigated. Also an attempt is made to modify the crystalline phase of the host polymer by low energy ion beam (Oxygen ion, O+1 with energy 100 keV) irradiation. These observations place ion irradiation as an effective tool in improving ionic conductivity in SPEs. Using X-ray diffraction spectra and the temperature dependent conductivity studies of SPEs, the effect of mixed ions and ion irradiation on the ionic conductivity of SPEs is investigated and presented.

Ion Transport and Materials Characterization Studies on Hot-Press Cast Zn2+ Conducting Nano-Composite Polymer Electrolyte (NCPE) Films: [90 PEO: 10 Zn (CF3SO3)2] + xAl2o3

Investigations on ion-transport and materials properties of poly (ethylene oxide) (PEO) based Zn2+ conducting Nano-Composite Polymer Electrolyte (NCPE) membranes: [90 PEO: 10 Zn (CF3SO3)2] + xAl2O3, have been reported. NCPE films have been prepared by a completely dry hot-press cast technique using Solid Polymer Electrolyte (SPE) composition: [90 PEO: 10 Zn (CF3SO3)2] as I phase and Al2O3 nano-filler particles (< 50 nm) as II- Phase dispersoid. In an earlier study, SPE used here as I phase host has been identified as optimum room temperature conducting film exhibiting (srt) ~1.01 x 10-5 S/cm. As a consequence of fractional dispersal of nano-filler particles in SPE, additional srt enhancement of an order of magnitude was obtained. This has been referred as NCPE OCC film. Ion transport behavior in NCPE OCC has been characterized in terms of ionic conductivity (?), total ionic (tion)/cation (t+) transport numbers which have been measured using different ac/dc techniques. Temperature dependent conductivity study has also been carried out to understand the mechanism of ion transport and to compute activation energy (Ea) from ‘log s-1/T’ plot. Materials and thermal properties have been characterized with the help of SEM, XRD, FTIR and DSC / TGA techniques.

Effect of neodymium doping on electrical properties and relaxor ferroelectric behavior of YCrO3 nanoparticles

In this research paper we have discussed the electrical, relaxor ferroelectric and ferromagnetic properties of Neodymium (Nd) doped YCrO3 nanomaterial prepared by sol-gel method. The characterization of the samples is followed by X-ray diffraction (XRD) and Transmission electron microscope (TEM). Upon Nd doping the conductivity of the YCrO3 enhances and the samples show semiconducting behavior. It is also found that the dc activation energy is decreased with the increasing doping concentration. Dielectric permittivity supports the modified Cole-Cole model with dc conductivity contribution correction. Both the space charge and free charge carrier dependent conductivity values increase with the increase of doping content. The frequency dependent conductivity study suggests the Dyre's free energy barrier model. Diffused relaxation peak has been observed in different doped samples. The diffuseness factor γ increases with increasing Nd doping concentration. Enhanced relaxer ferroelectric behavior has been noticed with the increasing Neodymium doping content in YCrO3.

Impedance spectroscopy studies on samarium and sodium substituted strontium bismuth titanate (SBTi)

Abstract Sr 1-x Sm x Na x Bi 4 Ti 4 O 15 lead-free piezoelectric ceramics are prepared by solid-state sintering method using high energy Ball- Mill and ground for 10 h. The single phase of the compound is confirmed by X-ray Diffraction and highest intensity peak (1 1 0) is observed at 30°. Diffraction peaks shifted towards higher angles with an increasing concentration of Sm 3+ and Na 1+ of SBT. Grains orientation and grain size are analyzed by Scanning Electron Microscope. Temperature and frequency dependent AC conductivity studies are carried out using impedance spectroscopy in the temperature range of 30 °C–650 °C using Wayn-Kerr LCR meter. At lower frequencies, conductivity is independent of frequency. The variation of Z″ with frequency shows peaks shifting towards higher frequencies with an increase of temperature. The resistance of grains (R g ), grain boundaries (R gb ) are calculated and it is found that grain resistance is greater than grain boundary resistance (R g > R gb ). Relaxation times of grain and grain boundaries are calculated.

Transport and Diffusion Properties in PEO-BaCl2 Polymer Electrolytes for Battery Applications

Barium chloride (BaCl2) doped polyethylene oxide (PEO) based solid polymer electrolyte (SPE) films are prepared using solution cast technique. Impedance analysis reveals that the ionic conductivity of pure PEO polymer enhances with frequency as well as BaCh concentrations, the maximum ac - ionic conductivity (1.09 × 10−4 Scm1) is observed at 10 wt% BaCl2 doped PEO polymer electrolyte films at high frequency. The temperature dependent conductivity studies were carried out for 10 wt% of BaCl2 concentration, here the maximum dc - ionic conductivity achieved is 1.44 × 10−2 Scm−1 at 333K temperature. From transport properties, it is observed that the transference number of ions in the polymer electrolyte system is 0.98 and electronic transference number are 0.019. Hence ions are the majority charge carriers than the electrons in BaCl2 doped PEO based solid polymer electrolytes. Diffusion coefficient study confirms the cations play a major role for the conduction mechanism with in the electrolyte system.

Synthesis, growth, optical, mechanical and dielectric studies on NLO active monometallic zinc iodate [Zn(IO3)2] crystal for frequency conversion

The monometallic single crystal of zinc iodate [Zn(IO3)2] was grown by slow cooling technique with the dimension up to 14 × 4 × 3 mm3 in the period of 35–45 days. Single crystal X-ray diffraction (XRD) analysis shows that the zinc iodate (ZI) crystal crystallizes in monoclinic crystal system with space group P21. The various functional groups of ZI were identified by FTIR analysis. The optical absorption of the grown crystal has been ascertained by UV–vis-NIR absorption studies. Second harmonic generation (SHG) efficiency of ZI is 2.75 times greater than that of KDP sample. The microhardness test of the grown crystal suggests that the crystal possesses relatively high mechanical strength. From the mechanical test certain mechanical parameters were determined. The dielectric behavior of the ZI crystal at different temperatures with varying frequencies shows the normal behavior activity of the grown crystal. The field dependent conductivity study was carried out.

High dielectric constant and relaxor behavior in La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 manganite

The dielectric properties of La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 (LSNMTi0.2) were investigated as a function of temperature and frequency. Compared with the dielectric constants of most ferroelectric and relaxor materials, in this compound we have found a colossal dielectric constant phenomenon consisting in a low frequency dielectric constant ε″ over 106 around room temperature. However, Frequency and temperature dependent ac conductivity and complex impedance studies were linked to semiconducting grains and insulating grain boundaries, which support the non-Debye type of relaxation in the polycrystalline sample. Furthermore, decrease in the resistive properties with an increase in temperature, explained in terms of the mobility of the charge carriers, signaled the semi-conductor behavior with negative temperature coefficient of resistance (NTCR). The scaling behavior of the Modulus spectra M″ versus frequency allowed us to understand whether the short-range or the long-range movement of charge carriers is the dominant in relaxation process, confirming the non-Debye type of multiple relaxations in the system. The variation in the dielectric permittivity, explained in terms of the space charge polarization according to the Maxwell–Wagner model and the Koop's phenomenological theory and the large dielectric response, was induced by the barrier layers in the grain boundaries and the mixed-valent structures of Mn3+/Mn4+ and Ti4+/Ti3+.