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Mahesh Kumar

Bio: Mahesh Kumar is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Molecular beam epitaxy & Heterojunction. The author has an hindex of 29, co-authored 204 publications receiving 4864 citations. Previous affiliations of Mahesh Kumar include Indian Institutes of Technology & Indian Institute of Technology Delhi.


Papers
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TL;DR: This corrects the article DOI: 10.1038/srep36132 to indicate that the author of the paper is a doctor of medicine rather than a scientist, as previously reported.
Abstract: Scientific Reports 6: Article number: 36132; published online: 31 October 2016; updated: 26 June 2017. This Article contains errors. The Acknowledgements section is incomplete. “We thank the Department of Biotechnology (DBT), Government of India for research support to the Institute of Bioinformatics (IOB), Bangalore.

839 citations

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TL;DR: In this paper, the phase pure BiFeO3 was synthesized using the oxide mixing technique followed by leaching with dilute nitric acid, and X-ray diffraction pattern indicated that the sample is phase pure.
Abstract: The difficulties in synthesizing phase pure BiFeO3 are well known. In this letter we are reporting the optimized synthesis conditions for obtaining phase pure BiFeO3 ceramic. The oxide mixing technique followed by leaching with dilute nitric acid has been used for the synthesis. X-ray diffraction pattern indicated that the sample is phase pure. Scanning electron microscopy along with energy dispersive x-ray fluorescence analysis confirmed the chemical homogeneity of the sample. No segregation of the impurity phase in the matrix was detected. Moreover, Bi/Fe atomic ratio is observed to be ∼1. The ferroelectric transition of the sample at 836 °C has been detected by differential thermal analysis.

738 citations

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TL;DR: In this article, the relaxation time of BiFeO3 was estimated using the relaxation times of the intermediate compositions of the BaTiO3 mixture, and the authors showed that the capacitance observed is from the bulk of the sample.
Abstract: BiFeO3, when forming a solid solution with BaTiO3, shows structural transformations over the entire compositional range. Above 70 mole % of BiFeO3 the structure is rhombohedral and below 4 mole %, it is tetragonal. In between the structure is cubic. The ferroelectric TC decreases with increasing composition of BaTiO3 and a relatively small relaxation is observed. Impedance measurements showed a structural dependence and analysis of which has clearly shown that the capacitance observed is from the bulk of the sample. Relaxation time (τ) of BiFeO3 was estimated using the relaxation times of the intermediate compositions. Magnetization measurements showed field induced ferromagnetism. As the structure becomes cubic with increasing concentration of BaTiO3, paramagnetism sets in, as evidenced by the electron spin resonance spectra.

463 citations

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TL;DR: In this paper, several techniques related to the synthesis of ZnO nanostructures and their efficient performance in sensing are reviewed, such as functionalization of noble metal nanoparticles, doping of metals, inclusion of carbonaceous nanomaterials, using nanocomposites of different MO x, UV activation, and post-treatment method of high-energy irradiation on ZnOs, with their possible sensing mechanisms.

323 citations

Journal ArticleDOI
TL;DR: The demonstrated ultrafast detection and reversible MoS2 gas sensor at room temperature shows reliable selectivity toward NO2 against various other gases and reveals the potential of 2D MoS 2 to develop a low power portable gas sensor.
Abstract: Two-dimensional materials have gained considerable attention in chemical sensing owing to their naturally high surface-to-volume ratio. However, the poor response time and incomplete recovery at room temperature restrict their application in high-performance practical gas sensors. Herein, we demonstrate ultrafast detection and reversible MoS2 gas sensor at room temperature. The sensor’s performance is investigated to NO2 at room temperature, under thermal and photo energy. Incomplete recovery and high response time of ∼249 s of sensor are observed at room temperature. Thermal energy is enough to complete recovery, but it is at the expense of sensitivity. Further, under photo excitation, MoS2 exhibits an enhancement in sensitivity with ultrafast response time of ∼29 s and excellent recovery to NO2 (100 ppm) at room temperature. This significant improvement in sensitivity (∼30%) and response time (∼88%) is attributed to the charge perturbation on the surface of the sensing layer in the context of NO2/MoS2 i...

314 citations


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7,335 citations

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TL;DR: In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented, ranging from atom to phase diagram, and the current development stage in lead free piezoceramics is then critically assessed.
Abstract: A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

2,510 citations

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TL;DR: In this article, a single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique.
Abstract: Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

970 citations

Journal ArticleDOI
Ling Zhu1, Wen Zeng1
TL;DR: In this paper, the room-temperature gas sensing properties of ZnO-based gas sensors are comprehensively reviewed, and more attention is particularly paid to the effective strategies that create room temperature gas sensing, mainly including surface modification, additive doping and light activation.
Abstract: Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.

756 citations