An International Research Journal

Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)201-204


Electrical Properties of La Modified Tungsten Bronze Vanadates

 

P S Sahoo, B B Mohanty, R N P Choudhary

aDepartment of Physics, Betnoti College, Betnoti, Mayurbhanj, Orissa, India

bDepartment of Physics, ITER, Bhubaneswar

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Lanthanum-doped strontium vanadates, Sr5LaTi3V7O30, were prepared by a high-temperature sold-state reaction method. The formation of the materials was checked by X-ray diffraction technique. Preliminary structural analyses of the materials exhibit the formation of single-phase orthorhombic structures. Surface morphology of the compounds was studied by scanning electron microscopy. The effect of La on microstructure of the materials has resulted in a modification of the electrical properties. Study of electrical properties using impedance analysis technique exhibit;
(i) the presence of negative temperature coefficients of resistance behavior, (ii) presence of temperature dependent electrical relaxation phenomena, (iii) evidences of single electrical relaxation attributed to the presence of bulk contribution to the electrical properties, (iv) an enhancement in the barrier to the mobility of charge carriers on La-substitution.

Keywards: X-ray diffraction; Phase transitions; Dielectric loss and relaxation

PACS: 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.80.Bh

Total Ref : 9 

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)205-210

 

Structural and electrical properties of Sr modified Rare earth doped ceramics

 

BB Mohanty, P S Sahoo, R N P Choudhary

aDepartment of Physics, Betnoti College, Betnoti, Mayurbhanj, Orissa, India

bDepartment of Physics, ITER, Bhubaneswar

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The polycrystalline sample of Sr5GdTi3V7O30, 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 (32- 400°C) and frequency (102–106 Hz) on electrical properties were studied using an impedance analyzer. A typical negative temperature coefficient of resistance (NTCR) behavior has been observed in this material.

Keywards: X-ray diffraction; SEM; Electrical conductivity

PACS: 77.22.Ch; 77.22.Ej; 77.22.Gm; 77.80.Bh

Total Ref : 15

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)211-217


Structural, electrical and multiferroic behavior of nanoparticles BiFeO3

 

Sangram Keshari Pradhan and Binod Kumar Roul

Institute of Materials Science, Planetarium Building, Bhubaneswar-751013, India

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Impurity free Monophasic rhombohedral BiFeO3 (BFO) nanoparticles are synthesized chemically by low cost pyrophoric reaction technique. The effect of synthesis route and particle size on structural, electrical and magnetic behavior of BFO ceramics were studied. From XRD analysis it is observed that solid state route prepared BFO sample showed rhombohedral structure (R3c) alongwith some higher order impurity phases, which become suppressed significantly with decrease of particles size to few nanometers. The dielectric and leakage current of the sample of nanoparticles BFO showed interesting results as compared to bulk BFO and over improved significantly. The ferroelectric hysteresis loops change its shape from rounded to a typical ferroelectric feature with improved remnant as well as saturation polarization value with particle size down to nanometer scale. Furthermore, BFO nanoparticles also showed a good ferromagnetic M-H hysteresis loop with enhanced saturation magnetization value.

Keywards: ceramics; leakage current; ferroelectricity; ferromagnetism

Total Ref : 17

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)219-224

 

Design of a holograting to couple power between two fibers for optical communication


Swati Mishra, S K Tripathy and Mihir Hota

National Institute of Science and Technology, Berhampur-761 008, Odisha, India

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Coupling of power in fiber optics communication is one of the important and challenging tasks. Several conventional methods for coupling are in uses which have their own merits and demerits. Recently coupling of power using Holographic technique is proposed. We in this paper investigated the design of an effective Coupler based on Hologram diffraction efficiency. It is found that, by increasing the refractive index modulation the thickness of the coupler can be decreased without affecting the diffraction efficiency. The design procedure for such a Holographic grating is also explained.

Keywards: Holograting, Diffraction efficiency, Recording geometry, Reconstruction geometry

Total Ref : 12

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)225-232


Complex impedance study of NaSr2Nb5O15 ceramic


S K Satpathy1, N K Mohanty1, Banarji Behera1, P Nayak1 and R N P Choudhary2

1Materials Research Laboratory, School of Physics, Sambalpur University,
Jyoti Vihar, Burla - 768 019, Odisha, India

2Department of Physics, ITER, Siksha 'O' Anusandhan University, Bhubaneswar – 751 030, India

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The polycrystalline sample of NaSr2Nb5O15 (NSN), which belongs to one of the important tungsten bronze family, was prepared by a high-temperature solid state reaction technique. Preliminary X-ray structural analysis exhibits the orthorhombic crystal structure of at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (102-106Hz) at different temperatures (28-5000C). The Nyquist plot reveals the presence of bulk effect and the bulk resistance deceases with rise in temperature. The imaginary part of impedance with frequency at various temperatures suggests the presence temperature dependent relaxation process in the sample. The dc conductivity is found to increase with rise in temperature which follows the Arrhenius law and the activation energy is found to be 0.88 eV.

Total Ref : 19

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)233-240


Studies of structural and dielectric properties of layered bismuth oxide: BaBi2V2O9


N K Mohanty, R N Pradhan, B Behera and P Nayak

Material Research Laboratory, School of Physics, Sambalpur University, Jyoti Vihar,Burla-768 019, Odisha, India 

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The polycrystalline sample of BaBi2V2O9 (BBV) belonging to the family of Aurivillius type was prepared by solid state reaction technique. The X-ray diffraction study of the prepared sample BBV reveals the orthorhombic crystal structure at room temperature. The studied sample has a dielectric anomaly at 95°C. The temperature dependent impedance parameters were investigated using an impedance analyzer in a wide range of frequencies (102-106Hz) at different temperatures. The Nyquist plots of the sample reveal the presence of only bulk effect. The bulk resistance of the sample decreases with increase in temperature which indicates the negative temperature coefficient of resistance (NTCR) behavior of the material. Further from the Dynamic Light Scattering (DLS) and Electrophoretic Light Scattering (ELS) studies it is observed that the particles show excellent aqueous dispersion stability without any change in hydrodynamic size and zeta potential.              

Keywords: Solid state reaction; XRD; Dielectric Properties; Impedance; Zeta Potential

Total Ref : 16

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)241-247


Anisotropy in layered NbS2 in terms of transport parameters


A Pattanaik1* and P Nayak1

1School of Physics, Sambalpur University, Jyoti Vihar, Burla, India, 768 019 


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Transition metal dichalcogenides 2H-MX2 (M=Nb, Ta, X= S, Se) are materials with layered structure. These structures show large anisotropy in electrical, optical, magnetic and transport properties. Particularly, NbS2 shows large anisotropy not undergoing a charge density transition but is extreme type-II superconductor for lower applied field remaining in the mixed state. In view of this, in lower applied field limit, the order parameter is assumed to be spatially constant and the vortex cores are treated as singularities. Using the anisotropic formulation of the London limit for the two applied field directions, we have tried to explain the temperature dependence of change in specific heat. The anisotropic ratio g has also been calculated in terms of in plane and out plane penetration depths and found a qualitative agreement with the experimental findings.

Total Ref : 20

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Asian Journal of Physics                                                                                                         Vol. 21, No 2 (2012)249-254


Study of elastic constants in heavy fermions (HF) systems: A small q and T analysis 


N Shadangi1, J Sahoo2 and P Nayak3

1Padmashree Krutartha Acharya College of Engineering, Bargarh,Odisha

2Regional office of vocational Education, Sambalpur768001, Odisha

3School of Physics, Sambalpur University,Jyoti Vihar, Burla-768019,Sambalpur, Odisha 

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The effect of electron- phonon interaction and the temperature dependence of elastic constants in Heavy Fermion (HF) systems are analyzed for finite wave vector q and finite temperature T. The reduced value of the elastic constant (=C/C0) is evaluated through Periodic Anderson Model (PAM) in presence of electron-Phonon interaction using Zubarev type double time temperature dependent Green function. The calculated renormalized elastic constants is analyzed for different system parameters like effective coupling strength 'g', the position of f-level 'd' and the onsite coulomb interaction 'U'. The results obtained are found to give good agreement with the general features observed experimentally for CeAl3 HF system.

Total Ref : 10

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