Keywords : Conductivity


Percolation-induced low frequency plasmonic state in metal granular composite materials

Takanori Tsutaoka; Herieta Massango; Teruhiro Kasagi

Advanced Materials Letters, 2018, Volume 9, Issue 7, Pages 476-480
DOI: 10.5185/amlett.2018.2053

Low frequency plasmonic (LFP) state induced by the electrical percolation of metallic particles has been investigated for metal granular composite materials containing Cu, Ni47Fe53 and Co50Fe50 microparticles. In these composites, a conductivity jump due to electrical percolation takes place at different particle volume fraction j; a conductive state is established above the percolation threshold jC. The jC is 0.16 for Cu, 0.61 for Ni47Fe53, and 0.76 for Co50Fe50 composites, respectively. In the Cu composite, the LFP state takes place in the conductive state just above jC. However, in the Ni47Fe53 composite, the LFP state is established at j = 0.90; the LFP state couldn’t be observed in the Co50Fe50 one. Hence, a non-plasmonic conductive state can exist in the percolated state; the LFP state can be established in the conductive state with about 1.0 S/cm of the conductivity value. 

Impact Of Cross Linking Chain Of N,N’-bis(napthalen-|-y|)-N,N’-bis(phenyl)-benzidine On Temperature dependent Transport Properties

M. Ramar; S. S. Rawat; R. Srivastava; S. K. Dhawan; C. K. Suman

Advanced Materials Letters, 2016, Volume 7, Issue 10, Pages 783-789
DOI: 10.5185/amlett.2016.6305

The impact of cross linking chain of N, N’-bis (napthalen-|-y|)-N, N’-bis(phenyl)-benzidine (NPB) was studied for opto-electrical properties having focus on temperature dependent transport properties. The Spiro structured NPB compound is closed in itself and the thin film surface roughness is less in comparison to NTNPB compounds. Both absorptions and photoluminence shows a shift of 10 nm towards higher wavelength in case of cross linked spiro structured compound. The mobility calculated in SCLC region for NT and Spiro NPB was 1.32×10 -7 and 3.3x10 -7 cm 2 V -1 s -1 , respectively. Both the compounds show single relaxations and can be modeled as an RC equivalent circuits. The dc conductivity for both the compounds was explained by Mott’s VRH models showing 3D transport mechanism. The hopping distance for NT and Spiro NPB compounds is 0.8 and 0.5 nm, respectively. The hopping conduction process can be explained clearly using correlated barrier hopping model. The cross linking of the compounds shows two orders of less density of states.

Preparation, Characterization And Dielectric, Ac Conductivity With Electrochemical Behavior Of Strontium Zirconate

Rohan Dasa; Kaushik Guptaa; Kuntal Janaa; Arabinda Nayakb; Uday Chand Ghosha

Advanced Materials Letters, 2016, Volume 7, Issue 8, Pages 646-651
DOI: 10.5185/amlett.2016.6294

Strontium-zirconium bimetal oxide (SrZrO3) samples at nanophase were prepared by chemical precipitation-annealnation method, and characterized by powder X-ray diffraction (XRD), UV-Vis and FTIR spectroscopies and field emission scanning electron microscopy (FESEM). Grain size (nm) of the SrZrO3 samples prepared by annealing at 650°C (S650), 850°C (S850) and 1050°C (S1050), respectively, were 55-60, 45-47 and 25-32. The optical band gaps (eV) estimated are to be 4.71 and 4.83 of S850 and S1050, respectively. Both FTIR and XRD studies confirmed the formation of SrZrO3 phase. FESEM images of the S850 sample showed the presence of agglomerated nano spheres with irregular surface morphology. Temperature dependent ac-conductivity analyses of S850 sample showed semiconducting behavior with low thermal activation energy (28 meV). Hopping conduction of charge carriers had been concluded considering the relaxation processes associated with the grain and grain boundaries of the sample. Dielectric behavior of S850 sample was confirmed from considerably high dielectric constant value (~ 140) and low dielectric loss (~ 0.6) at 100 Hz. Cyclic voltammograms suggested the pseudo-capacitive behavior of as-prepared S850 and S1050 samples. Thus as-prepared SrZrO3 nanophase could be used as High-K dielectric material in various applications.

Microstructural And Dielectric Investigations Of Vanadium Substituted Barium Titanate Ceramics

Aditya Jain; Neelam Maikhuri; Rakesh Saroha; Mukul Pastor; A. K. Jha; A. K. Panwar

Advanced Materials Letters, 2016, Volume 7, Issue 7, Pages 567-572
DOI: 10.5185/amlett.2016.6172

In this investigation, the microstructural and dielectric properties of pure BaTiO3 and vanadium (V 5+ ) substituted on Ba 2+ site (A-site) and Ti 4+ site (B-site) in BaTiO3 ceramic have been studied. The three compositions of BaTiO3 (BT), Ba0.9V0.1TiO3 (BTA) and BaTi0.9V0.1O3 (BTB) were synthesized using solid-state reaction route. The XRD analysis of all three compositions has been carried out at room temperature and proper phase formation for BT, BTA and BTB are confirmed. However, compositions BTA and BTB indicate the presence of secondary phases, and it may be due to higher amount of vanadium substitution at A and B sites. Addition of vanadium inhibited the grain growth of BaTiO3 ceramic. Vanadium substitution on A- and B-site have resulted in decrease of Curie temperature as well as dielectric loss compared to pure BT. A more diffused behavior is observed in vanadium substituted samples as compare to pure BT which shows a sharp transition and lower value of diffuseness parameter. Impedance study shows that substitution of vanadium on A- as well as B-site results in decrease of AC conductivity. These properties of vanadium substituted samples can be utilized to reduce the dielectric loss in capacitors and in radio frequency applications.

Facile Room Temperature Ion Exchange Synthesis Of H+ Doped KM0.33Te1.67O6 (M = Al, Cr And Fe) And Their Photocatalytic And Conductivity Studies

Ravinder Guje; G.Ravi;M. Vithal; J.R. Reddy; Ch. Sudhakar Reddy; K. Sreenu; G.Ravi and M. Vithal

Advanced Materials Letters, 2016, Volume 7, Issue 7, Pages 536-541
DOI: 10.5185/amlett.2016.6073

Materials belonging to defect pyrochlore structure have been the subject of considerable interest and expected to exhibit fast protonic conduction. The proton exchanged ternary metal oxides of composition HM0.33Te1.67O6 (M = Al, Cr and Fe) are prepared for the first time by ion exchange method at room temperature. These materials are characterized by X-ray Diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and solid state NMR techniques. All the materials are crystallized in a cubic lattice with the Fd - 3m space group. Photocatalytic activity against methyl violet (MV) degradation under visible light irradiation is studied. The mechanistic degradation pathway of MV is studied by a fluorescence technique using terepthalic acid (TA) as a probe and Tertiary butanol (TB) as hydroxyl radical quencher. The dc conductivity of all three compositions is studied in the temperature range 300 – 673 K. The variation of dc conductivity with temperature is explained.

Improvements In Electronic Structure And Properties Of Graphene Derivatives

Velram Balaji Mohan; Manfred Stamm;Debes Bhattacharyya; Dongyan Liu; Krishnan Jayaraman

Advanced Materials Letters, 2016, Volume 7, Issue 6, Pages 421-429
DOI: 10.5185/amlett.2016.6123

This article focuses on the reduction of graphene oxides using different reductants and conditions systematically varying the chemical and physical structure, surface topography and chemistry and film thickness of reduced graphene oxide (rGO) films, with a focus on how these influence the property of most interest: electrical conductivity. The reduction process restores graphene oxide to a graphene-like structure, improving electrical conductivity while creating changes such as increased roughness, film thickness and new surface functionality. Films with smooth surfaces and minimal thicknesses have been shown to possess higher electrical conductivity. There have been minor changes in d-spacing and improvements in crystal perfection and orientation could be concluded from XRD patterns. Through XPS analysis, a significant decrease in the amount of oxygen functional groups at the surface has been noticed as the films get thinned. 

Electrical Conductivity, Mechanical Stability, Antibacterial And Anticancer Activities Of Ethyl Cellulose-tin(ll) Hydrogen Phosphate

Tanvir Arfin; Faruq Mohammad

Advanced Materials Letters, 2015, Volume 6, Issue 12, Pages 1058-1065
DOI: 10.5185/amlett.2015.5896

In the present study, a very prominent cost effective sol-gel method was used to amalgate the ethyl cellulose-tin(II) hydrogen phosphate (EC-SnHPO4), an organic–inorganic composite material with certain acidic condition practiced in a conductivity system. The physical characterization of the material was described by the UV-Vis and FTIR study. The different monovalent electrolytes such as KCl (aq) and NaCl (aq) at diverse temperature range was employed to measure the conductivity of EC-SnHPO4 and also for the concentration to explore between affinity of conductivity and electrochemical properties of the material. From the study, the conductivity was established to be less for K + than Na + . For such process in addition, the different parameters such as ionization potential, oscillator strength, transition dipole moment, resonance energy, and transition energy were investigated. Finally, the anticancer effect against the MCF-7 breast cancer cell line and the antibacterial activity against two different bacterial strains show the potential pharmacological activity of the EC-SnHPO4 towards medical applications.

Electrical And Polarization Behaviour Of Titania Nanoparticles Doped Ferroelectric Liquid Crystal

Swadesh Kumar Gupta; Dharmendra Pratap Singh; Rajiv Manohar*

Advanced Materials Letters, 2015, Volume 6, Issue 1, Pages 68-72
DOI: 10.5185/amlett.2015.5614

The present study focuses on the effect of anatase TiO2 (titania) nanoparticles (NPs) on conductivity and polarization in a ferroelectric liquid crystal (FLC). Different dielectric and electro-optical measurements have been conducted to explore the charge transportation and polarization mechanism in titania NPs doped FLC system. Doping of titania NPs show reduced dc conductivity of doped LC system attributed to the trapping of free charges by titania NPs at its surface. Polarization has been found to increase at low fields indicating reduction of field screening effect in doped FLC system. Optical response of the doped FLC system has been improved due to decreased intervention of ionic charges particularly at small electric fields. The present study will be helpful in minimizing the slow response problems and the grey level shift in liquid crystal devices which arise due to ionic effects.

Dielectric Relaxation And Electrical Properties Of ZnO1-xSx nanoparticle dispersed Ferroelectric Mesophase

Dharmendra Pratap Singh; A. C. Pandey;Rajiv Manohar; Swadesh Kumar Gupta

Advanced Materials Letters, 2013, Volume 4, Issue 7, Pages 556-561
DOI: 10.5185/amlett.2012.11463

The ZnO1-xSx, metal oxide nanoparticles (MNPs) have been dispersed in the ferroelectric mesophase (FLC). The electrical properties and dielectric relaxation processes have been studied for the MNPs dispersed FLC system with the variation of frequency and temperature. The dielectric measurements have been carried out in the frequency interval of 1Hz-10MHz to investigate different relaxation processes. Three different relaxation modes have been observed in the case of the pure FLC at frequency 2.5Hz, 20Hz and Goldstone relaxation mode at 200Hz. The addition of MNPs, suppressed the relaxation mode observed at 2.5 Hz for the pure FLC whereas the relaxation mode observed at 20 Hz is shifted to the higher frequency side. The conductivity and the relative permittivity of the pure FLC have also been enhanced by the dispersion of the MNPs. The present investigation establishes the MNPs as an intelligent material to tune the relaxation process and to enhance the conductivity of the materials.

Impedance Properties Of 0.7(BiFeO3)-0.3 (PbTiO3) Composite

Ajay Kumar Behera; Nilaya K. Mohanty; Banarji Behera; Pratibindhya Nayak

Advanced Materials Letters, 2013, Volume 4, Issue 2, Pages 141-145
DOI: 10.5185/amlett.2012.6359

The polycrystalline sample of 0.7(BiFeO3)-0.3(PbTiO3) [0.7(BFO)-0.3(PT)] was prepared by a high temperature solid state reaction technique. Studies of structural analysis confirm the formation of the compound with rhombohedral structure at room temperature. The electrical properties (impedance, modulus and conductivity) of the material were analyzed using a complex impedance spectroscopy technique in a wide temperature (225-300 o C) and frequency (10 2 -10 6 Hz) range. The studied material exhibits a significant contribution of grain (bulk) effect and non-Debye of relaxation process. The bulk resistance decreases with rise in temperature which exhibits negative temperature coefficient of resistance (NTCR) behavior. Electrical modulus study confirms the presence of bulk effect in the material. This compound also exhibits the temperature dependence of relaxation phenomena. The ac and dc conductivity of the materials were found to be increase with increase in temperature. The activation energy of the compound is found to be less than 1eV and suggests the conduction process is of mixed type (ionic-polaronic and singly-ionized oxygen ion vacancies).

AC impedance spectroscopy and conductivity studies of Ba0.8Sr0.2TiO3 ceramics

Subrat K. Barik; R.N.P. Choudhary; A.K. Singh

Advanced Materials Letters, 2011, Volume 2, Issue 6, Pages 419-424
DOI: 10.5185/amlett.2011.2228

The AC impedance and conductivity properties of Ba0.8Sr0.2TiO3 ceramics in a wide frequency range at different temperatures have been studied. The compound was prepared by a high-temperature solid-state reaction technique. A preliminary structural analysis of the compound by X-ray diffraction technique confirmed its single phase. An ac impedance spectroscopic technique was used to correlate between the microstructure and electrical properties of the compound. The presence of both grain (bulk) and grain boundary effect in the compound was observed. The frequency-dependent electrical data were used to study the conductivity mechanism. An analysis of the electric impedance and modulus with frequency at different temperatures has provided some information to support suggested conduction mechanism.

Fabrication Of Advanced Poly(etheretherketone)/ Clay Nanocomposites And Their Properties

R. K. Goyal; J.N. Sahu

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 205-209
DOI: 10.5185/amlett.2010.8151

High performance polymer nanocomposites based on poly(etheretherketone) (PEEK) as matrix and modified clay as reinforcement were fabricated using hot pressing at 380 °C and 45 MPa. The clay was varied from 0 to 5 wt%. Nanocomposites were characterized by X-ray diffraction (XRD), Vickers hardness tester, high resistivity meter, and impedance analyzer to get information about morphology, microhardness, electrical conductivity and dielectric properties of nanocomposites, respectively. The experimental density was very close to the theoretical density. XRD showed exfoliation of clay up to 3 wt% and intercalation for 5 wt% nanocomposite. The water absorption decreased by 38 % at 1 wt% clay content. The microhardness increased up to 12 % for 2 wt% clay nanocomposite. Electrical conductivity was increased two orders of magnitude higher than pure PEEK. Dielectric constant was increased slightly with increasing clay content. The significant improvement in properties at lower clay loading might be attributed to the exfoliation of clay in the matrix.

Polyphenylene Sulphide/graphite Composites For EMI Shielding Applications

Rajendra Kumar Goyal;Amol Kadam

Advanced Materials Letters, 2010, Volume 1, Issue 2, Pages 143-147
DOI: 10.5185/amlett.2010.7136

Electrical properties of graphite flake (GF) filled polyphenylene sulphide (PPS) composites prepared by hot pressing was investigated to be used for electromagnetic interference (EMI) shielding applications. Composites exhibited an electrical conductivity percolation threshold of 5 wt%. The electrical conductivity of composites was increased fourteen orders of magnitude higher than that of pure PPS. The dielectric constants and dissipation factor of composites were measured in a frequency range of 100 KHz to 15 MHz. The dielectric constant of the composites increased several orders of magnitude and showed a strong dependence on frequencies. For example, dielectric constant of 8 wt% composite measured at 1 MHz was increased by five orders of magnitude compared to pure PPS. Similarly, dissipation factor was increased significantly. Scanning electron microscopy showed 3-dimensional conducting network of GF across the PPS matrix. Significant improvement in electrical properties shows that these composites may be useful for EMI shielding particularly at high temperature applications.