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Singh K.,Indian Institute of Technology Roorkee | Singh S.K.,Solid State Physics Laboratory SSPL | Kaur D.,Indian Institute of Technology Roorkee
Ceramics International | Year: 2016

The current study explored the influence of Mn substitution on the electrical and magnetic properties of BiFeO3 (BFO) thin films synthesized using low cost chemical solution deposition technique. X-ray diffraction analysis revealed that pure rhombohedral phase of BiFeO3 was transformed to the tetragonal structure with P4mm symmetry on Mn substitution. A leakage current density of 5.7×10-4 A/cm2 which is about two orders of magnitude lower than pure BFO was observed in 3% Mn doped BFO thin film at an external electric field >400kV/cm. A well saturated (p-E) loops with saturation polarization (Psat) and remanent polarization (2Pr) as high as 60.34 μC/cm2 and 25.06 μC/cm2 were observed in 10% Mn substituted BFO thin films. An escalation in dielectric tunability (nr), figure of merit (K) and quality factor (Q) were observed in suitable Mn doped BFO thin films. The magnetic measurement revealed that Mn substituted BFO thin films showed a large saturation magnetization compared to pure BFO thin film. The highest saturation ~31emu/cc was observed for 3% Mn substituted BFO thin films. © 2016 Elsevier Ltd and Techna Group S.r.l. Source


Prakash S.,VHNSN College | Rajesh S.,Biomedical Research Laboratory | Rajesh S.,Mepco Schlenk Engineering College, Sivakasi | Singh S.K.,Solid State Physics Laboratory SSPL | And 4 more authors.
Talanta | Year: 2011

A highly sensitive NOx sensor was designed and developed by electrochemical incorporation of copper nanoparticles (CuNP) on single-walled carbon nanotubes (SWCNT)-polypyrrole (PPy) nanocomposite modified Pt electrode. The modified electrodes were characterized by scanning electron microscopy and energy dispersive X-ray analysis. Further, the electrochemical behavior of the CuNP-SWCNT-PPy-Pt electrode was investigated by cyclic voltammetry. It exhibited the characteristic CuNP reversible redox peaks at -0.15 V and -0.3 V vs. Ag/AgCl respectively. The electrocatalytic activity of the CuNP-SWCNT-PPy-Pt electrode towards NOx is four-fold than the CuNP-PPy-Pt electrode. These results clearly revealed that the SWCNT-PPy nanocomposite facilitated the electron transfer from CuNP to Pt electrode and provided an electrochemical approach for the determination of NOx. A linear dependence (r 2 = 0.9946) on the NOx concentrations ranging from 0.7 to 2000 μM, with a sensitivity of 0.22 ± 0.002 μA μM-1 cm-2 and detection limit of 0.7 μM was observed for the CuNP-SWCNT-PPy-Pt electrode. In addition, the sensor exhibited good reproducibility and retained stability over a period of one month. © 2011 Elsevier B.V. Source


Rajesh S.,Biomedical Research Laboratory | Rajesh S.,Mepco Schlenk Engineering College, Sivakasi | Sethy N.K.,Defence Institute of Physiology and Allied science DIPAS | Bhargava K.,Defence Institute of Physiology and Allied science DIPAS | And 3 more authors.
Sensor Letters | Year: 2011

An electrochemical highly sensitive nitrite (NO 2 -) and superoxide anion radical (O 2 •-) sensor was fabricated and developed based on an electrochemical deposition of manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) in polypyrrole (PPy) matrix on Pt electrode. The surface morphological image of MnTMPyP-PPy and PPy matrix on Pt electrode was obtained by scanning electron microscopy exhibiting microporous structure. The electrochemical behavior of the MnTMPyP-PPy-Pt electrode as sensor investigated by cyclic voltammetry revealed that the characteristic of MnTMPyP reversible redox peaks obtained at -0.12 V and -0.38 V versus Ag/AgCl respectively. The sensor electrode showed an excellent electrocatalytic nitrite oxidase and superoxide dismutase (SOD) activities. This electrochemical sensor exhibited a linear current response over the concentration range from 0.8 to 1000 μM, with a detection limit of 0.8±0.03 μM for NO 2 - 2 and a corresponding linear range from 0.6 to 1000 μM, with a detection limit of 0.6±0.02 μM for O 2 •-. In addition, the sensor displayed high sensitivity, good reproducibility and retained stability over a period of ∼4 weeks. This SOD-mimetic electrode was proved to be effective not only in detecting NO 2 - and O 2 •- independently but also in determining the concentrations of NO 2 - and O 2 •- simultaneously in in vitro systems. Copyright © 2011 American Scientific Publishers All rights reserved. Source


Prakash S.,VHNSN College | Rajesh S.,Biomedical Research Laboratory | Singh S.K.,Solid State Physics Laboratory SSPL | Bhargava K.,Defence Institute of Physiology and Allied science DIPAS | And 3 more authors.
Sensor Letters | Year: 2011

A novel highly sensitive electrochemical NO x sensor was designed and developed based on electrochemically incorporated manganese tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP) in ZnOpolypyrrole (PPy) nanocomposite on Pt electrode. The electrodes were characterized by SEM and EDX spectra indicating the PPy matrix, ZnO and MnTMPyP deposition. Further, the electrochemical behavior of the MnTMPyP-ZnO-PPy-Pt electrode as sensor investigated by cyclic voltammetry exhibited the characteristic MnTMPyP reversible redox peaks at -0.1 V and -0.29 V versus Ag/AgCl respectively. The MnTMPyP-ZnO-PPy-Pt electrode exhibited 2-fold enhanced electrocatalytic activity towards NO x compared to the MnTMPyP-PPy-Pt electrode. A linear response over the concentrations ranging from 0.8 to 2000 μM, with a detection limit of 0.8±0.02 μM for NO x was observed at the MnTMPyP-ZnO-PPy-Pt electrode. Here, the ZnO-PPy nanocomposite facilitated the electron transfer provided an electrochemical approach for the determination of NO x with high sensitivity, good reproducibility and retained stability over a period of one month. Copyright © 2011 American Scientific Publishers All rights reserved. Source


Singh K.,Indian Institute of Technology Roorkee | Singh S.K.,Solid State Physics Laboratory SSPL | Kaur D.,Indian Institute of Technology Roorkee
Journal of Applied Physics | Year: 2014

The strain mediated electrical and magnetic properties were investigated in PZT/Ni-Mn-In heterostructure deposited on Si (100) by dc/rf magnetron sputtering. X-ray diffraction pattern revealed that (220) orientation of Ni-Mn-In facilitate the (110) oriented tertragonal phase growth of PZT layer in PZT/Ni-Mn-In heterostructure. A distinctive peak in dielectric constant versus temperature plots around martensitic phase transformation temperature of Ni-Mn-In showed a strain mediated coupling between Ni-Mn-In and PZT layers. The ferroelectric measurement taken at different temperatures exhibits a well saturated and temperature dependent P-E loops with a highest value of Psat∼55 μC/cm2obtained during martensite-austenite transition temperature region of Ni-Mn-In. The stress induced by Ni-Mn-In layer on upper PZT film due to structural transformation from martensite to austenite resulted in temperature modulated Tunability of PZT/Ni-Mn-In heterostructure. A tunability of 42% was achieved at 290K (structural transition region of Ni-Mn-In) in these heterostructures. I-V measurements taken at different temperatures indicated that ohmic conduction was the main conduction mechanism over a large electric field range in these heterostructures. Magnetic measurement revealed that heterostructure was ferromagnetic at room temperature with a saturation magnetization of ∼123emu/cm3. Such multiferroic heterostructures exhibits promising applications in various microelectromechanical systems. © 2014 AIP Publishing LLC. Source

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