Chin-Shen. Lim; K. H. Teoh; H. M. Ng; Chiam-Wen Liew; S. Ramesh
Abstract
In this study, poly (vinyl alcohol) (PVA), lithium perchlorate (LiClO4) and nano-sized titanium oxide (TiO2) were employed as host polymer, dopant salt and inorganic filler respectively. The influence of the inorganic filler on ionic conductivity, structural and morphological properties of the polymer ...
Read More
In this study, poly (vinyl alcohol) (PVA), lithium perchlorate (LiClO4) and nano-sized titanium oxide (TiO2) were employed as host polymer, dopant salt and inorganic filler respectively. The influence of the inorganic filler on ionic conductivity, structural and morphological properties of the polymer matrix are investigated. Ionic conductivity of polymer electrolytes is measured by ac-impedance spectroscopy at ambient temperature. The polymer electrolyte exhibits the highest ionic conductivity of 1.26×10 -4 S cm -1 upon addition of 8 wt. % TiO2. Dielectric behavior proves that incorporation of nano-sized TiO2 particles shows a significant effect on the dielectric constant of the polymer electrolyte system. XRD analyses disclose that the addition of TiO2 reduces the crystallinity of the polymer electrolytes which enhances the flexibility of polymer chains.
Aditya Jain; Neelam Maikhuri; Rakesh Saroha; Mukul Pastor; A. K. Jha; A. K. Panwar
Abstract
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 ...
Read More
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.
A. N. Upadhyay; R. S.Tiwari; Kedar Singh
Abstract
The electrical and dielectric properties of 3 and 5 wt. % of multi-walled carbon nanotube (MWCNT) containing Se85Te10Ag5 glassy composites have been investigated in the frequency range 20 Hz to 2 MHz from room temperature to 387 K. It has been found that the electrical conductivity is enhanced by 6 to ...
Read More
The electrical and dielectric properties of 3 and 5 wt. % of multi-walled carbon nanotube (MWCNT) containing Se85Te10Ag5 glassy composites have been investigated in the frequency range 20 Hz to 2 MHz from room temperature to 387 K. It has been found that the electrical conductivity is enhanced by 6 to 9 orders of magnitude up to 5 wt. % of MWCNT content resulting in transition for insulating to conducting behaviour. The activation energies for all samples have also been evaluated from the Arrhenius plot of the DC conductivity which shows a decreasing trend up to 5 wt. % MWCNT content. The largest dielectric constant of 142 (almost 10 times greater than pristine Se85Te10Ag5 glassy alloy) has been observed for 5 wt. % of MWCNT content at room temperature in low frequency range. Therefore it can be inferred that the electrical and dielectric properties of the chalcogenide glasses can be altered by the admixing or doping of carbon nanotubes (CNTs). The enhanced dielectric constant and electrical conductivity can be attributed to interface effect between MWCNT and the glassy matrix.
G. T. Lamdhade; F. C. Raghuwanshi; R. M. Agrawal; V. M. Balkhande; T. Shripath
Abstract
The samples have been prepared in the form of pellets of SnO2 nanoparticles and synthesized via the liquid-phase co-precipitation technique. The ac electrical conductivity of samples is found to be frequency dependent. The dielectric constant increases with temperature and decreases with frequency of ...
Read More
The samples have been prepared in the form of pellets of SnO2 nanoparticles and synthesized via the liquid-phase co-precipitation technique. The ac electrical conductivity of samples is found to be frequency dependent. The dielectric constant increases with temperature and decreases with frequency of applied field. The semiconducting behavior of SnO2 nanoparticles have been studied from I-V characteristics. The characterization of samples has been studied by XRD, FESEM, UV-spectra and TG-DTA plot
C. Jayachandraiah; G. Krishnaiah
Abstract
Pure and erbium (1.30, 1.79, 2.83 and 3.53 at. %) doped ZnO nanoparticles are synthesized by wet chemical co-precipitation method. The synthesized samples are characterized by powder X-ray diffraction (XRD), energy-dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), Raman spectroscopy, ...
Read More
Pure and erbium (1.30, 1.79, 2.83 and 3.53 at. %) doped ZnO nanoparticles are synthesized by wet chemical co-precipitation method. The synthesized samples are characterized by powder X-ray diffraction (XRD), energy-dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), Raman spectroscopy, UV–visible diffusion reflectance spectroscopy (DRS) and LCR Impedance spectroscopy. The XRD measurements confirmed the hexagonal wurtzite structure of all samples and size of the particle is found to be decreased with Er content. TEM images show spherical shape with more agglomeration in Er doped ZnO nanoparticles. Raman spectra confirmed the hexagonal wurtzite structure of pure and Er doped ZnO nanoparticles with E2 (high) mode at 438 cm -1 and presence of other possible defects. UV visible DRS shows decrease in the band gap with increasing Er 3+ in ZnO host. Dielectric constant, dielectric loss factor and ac conductivity properties were decreased with Er dopant in tune with Maxwell -Wagner principle and surface-orientation polarizations.
Elena Emanuela Valcu (Herbei); Viorica Musat; Susanne Oertel; Michael P.M. Jank; Timothy Leedham
Abstract
Solution-processed high-k dielectric hybrid thin films prepared at temperatures below 200 o C represent a subject of increasing scientific interest satisfying current requirements for printable thin film transistors used in transparent flexible electronics. In this work, we propose a new approach ...
Read More
Solution-processed high-k dielectric hybrid thin films prepared at temperatures below 200 o C represent a subject of increasing scientific interest satisfying current requirements for printable thin film transistors used in transparent flexible electronics. In this work, we propose a new approach for the synthesis of new tantalum oxide-PMMA hybrid dielectric thin films at 160 o C by modified sol-gel method, using as precursors tantalum ethoxide cluster (Ta(OC2H5)5) and methyl methacrylate monomer (MMA). So far it has not been reported in situ formation of tantalum oxide nanocrystals in hybrid dielectric materials at this low temperature. Hybrid sols with 1:1 and 4:1 (Ta(OC2H5)5):MMA molar ratios were used for spin-coating of thin films. The thermal behavior of these sols was observed in order to optimize the post-deposition treatment of the films. The hybrid films were investigated by scanning electron microscopy (SEM) for thickness and morphology, by grazing incidence x-ray diffraction (GIXRD) and high-resolution transmission electron microscopy (HRTEM) for tantalum oxide phase formation. TaO2 single crystals with a diameter of about 2 nm embedded in an amorphous phase were identified. The dielectric properties of the hybrid thin films were derived from the characterization of Metal-Insulator-Metal (MIM) structures by current-voltage and capacitance-voltage measurements. I-V curves show a leakage current between 10 -12 and 10 -7 A and a constant capacitance in bias range ± 50 V. For films with 1:1 and 4:1 molar ratio, the leakage current density ranges between 10 -9 - 10 -3 A/cm 2 and 10 -9 - 10 -4 A/cm 2 , and the limit of the current density goes to an electric field of ±1.2 MV/cm and ±2.5 MV/cm, respectively. In the case of films with 1:1 molar ratio, the applied voltage was up to 70 V in positive domain and no breakdown was observed for the dielectric layer. These results show higher current density for a larger voltage range, than the characteristics leakage current values reported for PMMA (10 -8 A/cm 2 ) at 0.3 MV/cm. The value of the permittivity ranges between 3.5 and 7.5 at 1 MHz, depending on the tantalum alkoxyde: MMA molar ratio, suggesting very promising future of these hybrid dielectric thin films for the fabrication of transparent TFTs, which can serve for next generation of transparent and flexible electronic devices.
Subhash B. Kondawar; A. D. Dahegaonkar; V. A. Tabhane; D. V. Nandanwar
Abstract
With more than 100 million tonnes of fly ash produced in India, use of fly ash for the preparation of polyaniline – fly ash composites will in no way help in its bulk utilization. Still the authors have made an effort towards the better utility of fly ash by synthesizing polyaniline –fly ...
Read More
With more than 100 million tonnes of fly ash produced in India, use of fly ash for the preparation of polyaniline – fly ash composites will in no way help in its bulk utilization. Still the authors have made an effort towards the better utility of fly ash by synthesizing polyaniline –fly ash composites for electronic devices where the requirement of dielectric materials with good electrical conductivity. There is great challenge to use the waste of thermal power stations in the form of fly ash as reinforcement for the conducting polymers to be good dielectric materials. In this paper, we report the use of fly ash to prepare conducting polymer composite materials. In-situ polymerization of aniline was carried out in the presence of fly ash (FA) to synthesize conducting polyaniline–fly ash composites (PANI-FA) by chemical oxidation method. The PANI-FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt %) of fly ash in conducting polymer matrix. The surface morphology of these composites was studied by scanning electron microscopy (SEM). These composites were characterized by Scanning Electron Microscopy (SEM), X-Ray Diffractometry (XRD), Fourier Transform Infra-Red (FTIR) Spectroscopy to investigate surface morphology and structure of the composites. Thermal and frequency dependence dielectric properties of all the synthesized composites have been studied with the help of impedance analyzer. By incorporating fly ash into conducting polymers, dielectric constant of the composites was found to be improved as compared to that of pure conducting polymers. It was also noticed that the dielectric constant of all the composites found to be decreased with increasing frequency but increased with increasing temperature. The results obtained for these composites are of greater scientific and technological interest for good quality capacitors.
K. K. Bamzai; Rashmi Gupta; Shivani Suri; Vishal Singh
Abstract
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, ...
Read More
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X - ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker’s hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε/) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330ËšC in case of magnesium hydrogen phosphate to 310ËšC in case of cadmium magnesium hydrogen phosphate.
Satish Verma; Jagdish Chand;M. Singh
Abstract
Nanocrystalline Al3+ ions doped Mg0.2Mn0.5Ni0.3AlyFe2-yO4 compositions, where y=0.0, 0.05 and 0.10 have been synthesized by citrate precursor method. The X-ray diffraction (XRD) revealed that the ferrite has single phase cubic spinel structure. The calculated particle size from XRD data have been verified ...
Read More
Nanocrystalline Al3+ ions doped Mg0.2Mn0.5Ni0.3AlyFe2-yO4 compositions, where y=0.0, 0.05 and 0.10 have been synthesized by citrate precursor method. The X-ray diffraction (XRD) revealed that the ferrite has single phase cubic spinel structure. The calculated particle size from XRD data have been verified using transmission electron microscopy (TEM). TEM photographs show that the ferrite powders consist of nanometer-sized particle. It was observed that the particle size decreases as the non-magnetic Al content increases. A decrease in lattice parameter and saturation magnetization with increase in aluminium concentration was attributed to smaller ionic radius and weakening of exchange interaction. Dependence of Mössbauer parameters such as isomer shift, quadrupole splitting and hyperfine magnetic field on Al 3+ ions concentration have been discussed. Initial permeability ‘µi’, relative loss factor (RLF), saturation magnetization and remanent magnetization decreases with increasing substitution of Al 3+ ions. The dielectric constant and dielectric loss decreases with increase in non magnetic Al 3+ ions. The dielectric constant follows the Maxwell–Wagner interfacial polarization. The electrical conduction in these ferrites is explained on the basis of the hopping mechanism.
N. K. Singh; Pritam Kumar; Chandra Prakash
Abstract
Recently a new wave of interest has risen on complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline ceramics of Ba(Fe0.5Nb0.5)O3 (BFN) and its solid solutions 0.89Ba(Fe0.5Nb0.5)O3-0.11BaTiO3 ...
Read More
Recently a new wave of interest has risen on complex perovskite structure due to their wide use in fabrication of multilayer ceramic capacitors, electrostrictive actuators, and electromechanical transducers. The polycrystalline ceramics of Ba(Fe0.5Nb0.5)O3 (BFN) and its solid solutions 0.89Ba(Fe0.5Nb0.5)O3-0.11BaTiO3 (BFN-BT11) and 0.89Ba(Fe0.5Nb0.5)O3-0.11SrTiO3 (BFN-ST11) were fabricated by a solid-state reaction Method. Processing parameters such as calcination temperature, sintering temperature and sintering durations were optimized to get best dielectric properties. It was found that the above ceramics sintered at 1250°C for 6 hours exhibited maximum density and uniform microstructure. X-ray diffraction studies of the compound showed the formation of single-phase monoclinic crystal structure at room temperature. Surface morphology of the compounds was studied by Scanning electron microscope (SEM). The effects of BaTiO3 and SrTiO3 substitution on the structure and on the electrical and ferroelectric properties of Ba(Fe0.5Nb0.5)O3 samples have been studied by performing x-ray diffraction and dielectric measurements. The electrical properties of the samples were investigated in a frequency range of 100 Hz - 1 MHz and temperature range of 30-350 °C using complex impedance spectroscopic technique. The frequency-dependent electrical data are also analyzed in the framework of conductivity and impedance formalisms.