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Structural and Electrical Characteristics of Ba(Fe0.5Nb0.5)O3-SrTiO3 Ceramic System  [PDF]
Narendra Kumar Singh, Pritam Kumar, Ajay Kumar Sharma, Ram Naresh Prasad Choudhary
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.211213
Abstract: A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X-ray diffraction (XRD) technique. The X-ray structural analysis of BFN and BFN-ST ceramics, showed the formation of single-phase compound in the monoclinic system, which is a distorted structure of an ideal cubic perovskite. Careful examination of microstructures of the individual compounds of the system was done by the scanning electron micrograph (SEM), and confirms the polycrystalline nature of the systems. Detailed studies of dielectric and electrical impedance properties of the systems in a wide range of frequency (100Hz - 5MHz) and different temperatures (30°C-285°C) showed that these properties are strongly dependent on temperature and frequency.
Structural, Thermal and Electrical Property of Polycrystalline LaLiMo2O8  [PDF]
Sanjaya Brahma, Ram Naresh Prasad Choudhary, Awalendra Kumar Thakur, Srinivasarao Ajjampur Shivashankar
New Journal of Glass and Ceramics (NJGC) , 2012, DOI: 10.4236/njgc.2012.21002
Abstract: This research article reports electrical characterization of a rare earth molybdate based on combination of rare earth (La+3) and alkali (Li+) metal ions. The experimental observation suggests the negative temperature coefficient of resistance behavior of the material. The material has been prepared by standard solid state reaction method, where the synthesis conditions have been optimized by thermal analysis. A possible mechanism for the formation of the polycrystal-line LaLiMo2O8 is reported. A systematic analysis has been done to determine the crystal structure of the powder material and it was found that the powder material was crystallized to tetragonal unit cell structure. Electrical properties have been studied using a.c. impedance measurement. The temperature variation of electrical conductivity of the material shows typical Arrhenius behavior. The activation energy evaluated from conductivity data works out to be ~0.94 ev.
Impedance Spectroscopy of Ba5GdTi3V7O30  [PDF]
Bana Bihari Mohanty, Priyadarshini Sanghamitra Sahoo, Mohapatra Prakash Kumar Sahoo, Ram Naresh Prasad Choudhary, Ram Naresh Prasad Choudhary, Ram Naresh Prasad Choudhary, Ram Naresh Prasad Choudhary
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.35050
Abstract: The polycrystalline sample of Ba5GdTi3V7O30 , a member of tungsten bronze structural family, was prepared by a high-temperature solid-state reaction technique. A preliminary X-ray diffraction analysis suggests the formation of single-phase compound with orthorhombic structure. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (102- 106 Hz) at different temperatures. The real and imaginary part of complex impedance traces semicircle(s) in the complex plane. The temperature dependent plots reveal the presence of both bulk and grain boundary effects. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The modulus analysis suggests a possible hopping mechanism for electrical transport processes of the material. The nature of variation of dc conductivity suggests Arrhenius type of electrical conductivity.
Effect of Strontium Substitution on Impedance Properties of Ba5GdTi3V7O30 Ceramics  [PDF]
Bana Bihari Mohanty, Priyadarshini Sanghamitra Sahoo, Bala Krushna Giri, Jagata Nanda Panda, Ram Naresh Prasad Choudhary
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.94043
Abstract: A series of compounds Ba5-xSrxGdTi3V7O30 (x = 0 - 5), belonging to tungsten bronze family were prepared by a high-temperature solid-state reaction route. Using X-Ray diffraction technique and Scanning Electron Micrograph, the formation and surface morphology of the compounds were studied. The X-Ray diffraction study informs the formation of single-phase orthorhombic structures. The substitution of Sr ion with increasing concentration in the compounds as per formula resulted in a variation of the electrical properties. Study of electrical properties using impedance analyzer exhibits: 1) the presence of negative temperature coefficients of resistance (NTCR) behavior; 2) presence of temperature dependent electrical relaxation phenomena; 3) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties for pure Ba5GdTi3V7O30 compound; 4) an enhancement in the barrier to the mobility of charge carriers on Sr-substitution. The effects of Sr on changes in the electrical conductivity as a function of temperature at different frequency are described based on impedance spectrum analysis.
Preparation and Study of Dielectric and Electrical Conductivity of Ba5NdTi3V7O30 Ceramics  [PDF]
Jagatananda Panda, Bana Bihari Mohanty, Priyadarshini Sanghamitra Sahoo, Ram Naresh Prasad Choudhary
Open Access Library Journal (OALib Journal) , 2018, DOI: 10.4236/oalib.1104834
Abstract:
Ba5NdTi3V7O30 is a tungsten bronze structured ceramic sample, prepared by Solid State reaction route at high temperature (950℃). The room temperature XRD analysis confirms orthorhombic crystal structure of the compound. Dielectric peak is observed at ~460℃ showing the transition of the compound from ferroelectric to paraelectric phase. Appearance of hysteresis loop confirms the existence of ferroelectric properties in the materials. Different values of activation energy in different temperature regions of the ac conductivity versus inverse absolute temperature graph exhibit mixed type of conduction process in the compound (i.e., ionic-polaronic and space charge generated from the oxygen ion vacancies).
Sunspot Bright Points
Debi Prasad Choudhary,Toshifumi Shimizu
Physics , 2010, DOI: 10.1007/s11207-013-0306-8
Abstract: We used the flux calibrated images through the Broad Band Filter Imager and Stokes Polarimeter data obtained with the Solar Optical Telescope onboard the Hinode spacecraft to study the properties of bright points in and around the sunspots. The well isolated bright points were selected and classified as umbral dot, peripheral umbral dot, penumbral grains and G-band bright point depending on their location. Most of the bright points are smaller than about 150 km. The larger points are mostly associated with the penumbral features. The bright points are not uniformly distributed over the umbra but preferentially located around the penumbral boundary and in the fast decaying parts of umbra. The color temperature of the bright points, derived using the continuum irradiance, are in the range of 4600 K to 6600 K with cooler ones located in the umbra. The temperature increases as a function of distance from the center to outside. The G-band, CN-band and CaII H flux of the bright points as a function of their blue band brightness increase continuously in a nonlinear fashion unlike their red and green counterpart. This is consistent with a model in which the localized heating of the flux tube deplete the molecular concentration resulting the reduced opacity which leads to the exposition of deeper and hotter layers. The scatter in CaII H irradiance is higher compared to the G-band and CN-band irradiance. The light curve of the bright points show that the enhanced brightness at these locations last for about 15 to 60 minutes with the least contrast for the points out side the spot. The umbral dots near the penumbral boundary are associated with elongated filamentary structures.
Synthesis of Silver Nanoparticles in Photosynthetic Plants
Ram Prasad
Journal of Nanoparticles , 2014, DOI: 10.1155/2014/963961
Abstract: Nanobiotechnology is emerging as a field of applied biological science and nanotechnology. Synthesis of nanoparticles is done by various physical and chemical methods but the biological methods are relatively simple, cost-effective, nontoxic, and environmentally friendly methods. The present review focuses on the synthesis of nanoparticles with special emphasis on the use of plants parts for the synthesis process, its applications, and future prospectus. 1. Introduction Nanotechnology focuses mainly on the design, synthesis and manipulation of structure and size of the particles with dimensions smaller than 100?nm [1]. Nanotechnology combines the principles with physical and chemical procedures to generate nanosized particles with the specific function. Nanotechnology is now creating a growing sense of excitement in the life sciences especially biomedical devices and medicine. Nanoparticles exhibit completely new or improved properties based on specific characteristics such as size, shape, and orientation [2]. The biological synthesis of nanoparticles is a cost-effective and ecofriendly methods and has ability to replace the physical and chemical methods because these methods are toxic and costly. Consequently, nanomaterials have been synthesized using microorganisms and plant extracts. The use of plant extracts for synthesis of nanoparticles is potentially advantageous over microorganisms due to the ease of scaling up the biohazards and elaborate process of maintaining cell cultures [3, 4]. For the last two decades extensive work has been done to develop new drugs from natural products because of the resistance of microorganisms to the existing drugs [1]. Integration of nanoparticles with biological molecules has led to the development of diagnostic devices and important tools in cancer therapy. Biological methods can employ either microorganism cells or plant extracts for nanoparticles production. Biosynthesis of nanoparticles is an exciting recent addition to the large repertoire of nanoparticles synthesis methods and, now, nanoparticles have entered a commercial exploration period. Au, Ag, Zn, and Cu have been used mostly for the synthesis of stable dispersions of nanoparticles, which are useful in areas such as photocatalysis, diodes, piezoelectric devices, fluorescent tubes, laser, sensor, optoelectronics, photography, biological labeling, photonics, and surface-enhanced Raman scattering detection [5–7]. Moreover, the biocompatible and inert nanomaterials have potential applications in cancer diagnosis and therapy. Nowdays, nanotechnology methods
Universal Current-Mode Biquad Filter Using a VDTA  [PDF]
Dinesh Prasad, Data Ram Bhaskar, Mayank Srivastava
Circuits and Systems (CS) , 2013, DOI: 10.4236/cs.2013.41006
Abstract:

This paper presents a new current-mode single input multi output (SIMO) type biquad employing one voltage differencing transconductance amplifier (VDTA), two grounded capacitors and a single grounded resistor. The configuration realizes all basic filter functions (i.e. Low Pass (LP), High Pass (HP), Band Pass (BP), Notch (BR) and All Pass (AP)). The natural frequency (ω0) and bandwidth (BW) are independently tunable. The workability of proposed configuration has been verified using SPICE simulation with TSMC CMOS 0.18 μm process parameters.

Electronically Controllable Fully-Uncoupled Explicit Current-Mode Quadrature Oscillator Using VDTAs and Grounded Capacitors  [PDF]
Dinesh Prasad, Mayank Srivastava, Data Ram Bhaskar
Circuits and Systems (CS) , 2013, DOI: 10.4236/cs.2013.42023
Abstract:

An electronically controllable fully uncoupled explicit current-mode quadrature oscillator employing Voltage Differencing Transconductance Amplifiers (VDTAs) as active elements has been presented. The proposed configuration employs two VDTAs along with grounded capacitors and offers the following advantageous features 1) fully and electronically independent control of condition of oscillation (CO) and frequency of oscillation (FO); 2) explicit current-mode quadrature oscillations; and 3) low active and passive sensitivities. The workability of proposed configuration has been demonstrated by PSPICE simulations with TSMC CMOS 0.18 μm process parameters.

Properties of 16 Sunspots Observed with Hinode Solar Optical Telescope
Debi Prasad Choudhary,Gordon A. MacDonald,Toshifumi
Physics , 2010,
Abstract: We studied 16 sunspots with different sizes and shapes using the observations with the Hinode Solar Optical Telescope. The ratio of G-band and CaII H images reveal rich structures both within the umbra and penumbra of most spots. The striking features are the compact blob at the foot point of the umbra side of the penumbral fibrils with disk center-limb side asymmetry. In this paper, we present properties of these features using the spectropolarimetry and images in G-band, CaII and blue filters. We discuss the results using the contemporary models of the sunspots.
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