Browsing by Author "Lakshman Pandey"

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Analytical Impedance Spectroscopy: Basics and Applications
(CRC Press, 2023) Lakshman Pandey; Devendra Kumar; Om Parkash; Shukdev Pandey
This book introduces the subject of impedance spectroscopy starting from fundamentals through to latest applications in areas such as ceramics, piezoelectric, sensors, agriculture, food quality control, medical diagnostics, cancer research, and so forth. Within the ambit of impedance spectroscopy, plots simulated for useful equivalent circuit models, design of sample holder, necessary precautions to be taken during measurement are described. It further discusses development of softwares for analysis of experimental data and choice of the most appropriate equivalent circuit model. All the materials are supported by problems, answers, appendices and references. Features: Includes fundamentals, equivalent circuit modeling and analysis of data related to impedance spectroscopy. Presents experimental measurements in a nuts-and-bolts approach. Includes derivation of expressions for some selected models and values of immittance functions as frequency of measurements tend to zero and to infinity. Provides clear recipe for beginners for proceeding toward developing equivalent circuit models. Describes computer program for complex nonlinear least squares fitting with example of program IMPSPEC.BAS This book is aimed at senior undergraduate/graduate students and researchers in materials engineering, mechanical engineering, electrical engineering, chemical engineering, biomedical engineering, construction engineering, physics, chemistry, medical diagnostics, agriculture and dairy. © 2024 Lakshman Pandey, Devendra Kumar, Om Parkash and Shukdev Pandey.
ANOMALOUS DIELECTRIC BEHAVIOUR IN PbO-BaO-TiO//2-B//2O//3-SiO//2 GLASSES.
(Indian Ceramic Soc, 1986) Devendra Kumar; Om Parkash; Lakshman Pandey; R. Rajgopalan
Glass ceramics in this system show ferroelectric behaviour due to crystallisation of either BaTiO//3 or PbTiO//3 microcrystalline phase in the glass. The dielectric behaviour has been studied as a function of temperature at different frequencies. These glasses show a relatively high dielectric constant which increases slowly up to the glass transition temperature and thereafter it increases sharply showing an anomalous dielectric peak at around 680 K. The dielectrically soft local atomic configuration of randomly distorted TiO//6 octahedra remain identifiable in the glassy matrix. Strong dipolar forces between these units are responsible for the ferroelectric - paraelectric phase transition leading to an anomalous peak in dielectric constant versus temperature curve. The increase in dielectric constant is attributed to glass softening.
Dielectric and microstructural behaviour of BaTiO3 sintered in the presence of a crystallizable glass
(Kluwer Academic Publishers, 1989) Devendra Kumar; P.K. Sakharkar; Om Parkash; Lakshman Pandey
[No abstract available]
Dielectric and microstructural behaviour of strontium titanate borosilicate glass ceramic system
(Springer India, 1995) O.P. Thakur; Devendra Kumar; O.M. Parkash; Lakshman Pandey
65(SrO·TiO2)-35(2SiO2·B2O3) wt% glass was synthesized. Differential thermal analysis study shows one exothermic peak which shifts towards higher temperature with increasing heating rate. Glass ceramics prepared by controlled crystallization of strontium titanate borosilicate glass produce uniform distribution of crystallites in a glassy matrix. Attempt was made to crystallize strontium titanate phase in this glass ceramic. Different phases precipitated out during ceramization have been identified by X-ray diffraction. It appears that due to high reactivity of SrO with B2O3, strontium borate crystallizes as principal phase followed by TiO2 (rutile) and Sr3Ti2O7 phases. Dielectric constant of these glass ceramics was observed to be more or less temperature independent over wide range of temperatures with low values of dielectric constant and dissipation factor. © 1995 The Indian Academy of Sciences.
Equivalent circuit model of Ca1-xYxTi1-xCoxO3 using impedance spectroscopy
(2003) Rajesh Kumar Katare; Lakshman Pandey; O.P. Thakur; Om Parkash; Devendra Kumar
Computer simulated complex immittance spectra of model equivalent circuits involving resistive and capacitive elements are calculated. A comparison of experimentally obtained complex immittance plots of the system Ca1-xYxTi1-x CoxO3 (x = 0.05) with these simulated diagrams greatly facilitates the search for the most appropriate equivalent circuit representing the electrical properties of electronic ceramics.
Equivalent circuit models for electronic ceramics
(Springer India, 1995) Lakshman Pandey; O.M. Parkash; Rajesh K. Katare; Devendra Kumar
Complex immittance spectra of model equivalent circuits involving resistive and capacitive elements are calculated. A comparison of experimentally obtained complex immittance plots with these diagrams greatly facilitates the search for the most appropriate equivalent circuit representing the electrical properties of electronic ceramics. © 1995 The Indian Academy of Sciences.
Glass ceramics containing ferroelectric phases
(Springer India, 1986) Om Parkash; Devendra Kumar; Lakshman Pandey
Glass ceramics prepared by controlled crystallization of glasses produce fine dispersion of crystallites in a glassy matrix. Glasses containing a mjor portion of constituents of a ferroelectric phase produce crystallites of ferroelectric phase in glass through a suitable heat treatment. The amount of network former in the initial glass has a profound influence on its crystallization behaviour and microstructure of the resulting ferroelectric glass ceramics. The value of dielectric constant and the nature of ferroelectric to paraelectric transition depend on the crystallite size and volume fraction of the ferroelectric phase. These glass ceramics are transparent for crystallite size less than 0·1 μm and exhibit large quadratic-electro-optic effect. © 1986 Indian Academy of Sciences.
Preparation, structure and dielectric properties of the system Sr1-xLaxTi1-xNixO3
(Kluwer Academic Publishers, 1989) Om Parkash; Lakshman Pandey; Mukhesh Kumar Sharma; Devendra Kumar
Attempts have been made to synthesize the solid solution Sr1-xLaxTi1-xNixO3 for x≤0.50 and its electrical behaviour has been studied. It was found that a solid solution forms for compositions up to x=0.10. The structure remained cubic. These compositions exhibited dielectric relaxator behaviour. The average grain size in these materials was very small. © 1989 Chapman and Hall Ltd.