Nishad G. Deshpande

Semiconductor metal oxide compounds based gas sensors: A literature review

This paper gives a statistical view about important contributions and advances on semiconductor metal oxide (SMO) compounds based gas sensors developed to detect the air pollutants such as liquefied petroleum gas (LPG), H2S, NH3, CO2, acetone, ethanol, other volatile compounds and hazardous gases. Moreover, it is revealed that the alloy/composite made up of SMO gas sensors show better gas response than their counterpart single component gas sensors, i.e., they are found to enhance the 4S characteristics namely speed, sensitivity, selectivity and stability. Improvement of such types of sensors used for detection of various air pollutants, which are reported in last two decades, is highlighted herein.

Structural, dielectric and magnetic properties of nickel substituted cobalt ferrite nanoparticles: Effect of nickel concentration

Nickel substituted cobalt ferrite nanoparticles with composition Co1−xNixFe2O4 (0.0 ≤ x ≤ 1.0) was synthesized using simple, low temperature auto combustion method. The X-ray diffraction patterns reveal the formation of cubic phase spinel structure. The crystallite size varies from 30-44 nm with the nickel content. Porous and agglomerated morphology of the bulk sample was displayed in the scanning electron microscopy. Micro Raman spectroscopy reveals continuous shift of Eg and Eg(2) stokes line up to 0.8 Ni substitution. The dispersion behavior of the dielectric constant with frequency and the semicircle nature of the impedance spectra show the cobalt nickel ferrite to have high resistance. The ferromagnetic nature is observed in all the samples, however, the maximum saturation magnetization was achieved by the 0.4 Ni substituted cobalt ferrite, which is up to the 92.87 emu/gm at 30K.

Effect of the cation substitution on the structural, electrical and magnetic properties in the electron-doped manganites

ABSTRACT Effect of cation substitution on the structural, electrical and magnetic properties in an electron-doped perovskite manganites viz. La0.90Zr0.10MnO3 (Zr10) and La0.90Te0.10MnO3 (Te10) prepared by solid-state reaction is reported herein. XRD indicates that both samples are polycrystalline with rhombohedral crystal structure. The strong absorption in FTIR spectra at ∼615 cm−1 was of Mn-O bond, which gets slightly shifted due to different ionic radii of cations. A large resistivity with a slight increase in transition temperature in the case of Te10 than Zr10 indicates that the ‘Te’ doping stabilizes the ground state of double-exchange mechanism between the eg levels and t2g levels.