S. Bandyopadhyay

Bio: S. Bandyopadhyay is an academic researcher from University of Burdwan. The author has contributed to research in topics: Rietveld refinement & Microstructure. The author has an hindex of 6, co-authored 21 publications receiving 99 citations.

Microstructure and charge carrier dynamics in Dy substituted phase stabilized cubic Bi2O3

Abstract: Room temperature phase stabilization of cubic Bi2O3 has been achieved by adding Dy2O3 as the dopant, using a low temperature citrate-auto-ignition method. The samples were sintered at different temperatures retaining the cubic fluorite structure. Rietveld refinement of the X-ray diffraction profiles has given detailed microstructural information of the prepared samples. The transmission electron micrographs confirmed the presence of atomic planes as obtained from X-ray diffraction. The UV-Vis spectra show a red shift of the absorption peak with the increase in sintering temperature. Impedance spectroscopy studies of the samples exhibited thermally activated non-Debye type relaxation process. In addition, studies of the electrical conductivity have suggested the negative temperature coefficient of resistance (NTCR) behavior of the samples. The comparable values of activation energies, obtained from different parameters, indicated that the ions follow the same type of mechanism for conduction as well as for relaxation. The temperature independence of the mechanisms has been confirmed from scaling of different spectra. The correlation between structural and electrical properties of the samples has been discussed and interpreted accordingly.

Mechanosynthesis of Nanocrystalline Fully Stabilized bcc γ-phase of Bi2O3 without Any Additive: Manifestation of Ferroelasticity in Microstructure, Optical, and Transport Properties

Abstract: In the present work, polymorphic phase transformation of Bi2O3 nanoparticles by the mechanical alloying method has been investigated in detail X-ray diffraction study reveals that the room tempera

Oxygen Vacancies Boost δ-Bi2O3 as a High-Performance Electrode for Rechargeable Aqueous Batteries.

Abstract: Metal oxides as electrode materials are of great potential for rechargeable aqueous batteries. However, they suffer from inferior cycle stability and rate capability because of poor electronic and ionic conductivities. Herein, taking vertically orientated Bi2O3 nanoflakes on Ti substrates as examples, we find that the δ-Bi2O3 electrode with plenty of positively charged oxygen defects show remarkably higher specific capacity (264 mA h g–1) and far superior rate capability than that of α-Bi2O3 with less oxygen vacancies. Through pinpointing the existence form and the role of oxygen vacancies within the electrochemical processes, we demonstrate that oxygen vacancies in δ-Bi2O3 can not only promote electrical conductivity but also serve as central entrepots collecting OH– groups via electrostatic force effect, which has boosted the oxidation reaction and enhanced the electrochemical properties. Our work merits an excellent Bi2O3 negative electrode material via giving full play to the role of oxygen vacancies ...

Narrow Band Gap Observed in a Molecular Ferroelastic: Ferrocenium Tetrachloroferrate

Abstract: Due to the intriguing chemical variability and structure–property flexibility, molecular materials with striking multifunctional characteristics, including tunable physical, chemical, optical, and ...

Investigation of annealing effects on the physical properties of Ni0.6Zn0.4Fe1.5Al0.5O4 ferrite

Abstract: In the present study, the structural, morphological, electrical, and dielectric properties of Ni0.6Zn0.4Fe1.5Al0.5O4 annealed at 600 °C, 900 °C, and 1200 °C were investigated. The X-ray diffraction patterns confirmed the presence of the single-phase cubic spinel structure with the Fdm space group. The SEM images of Ni0.6Zn0.4Fe1.5Al0.5O4 nanoparticles demonstrated that these samples (Ni900 and Ni1200) were nano-sized and that the increase in annealing temperature enhanced the agglomeration rate. It was found that the electrical conductivity of the system improved on increasing the temperature over the whole explored range for the two low annealing temperatures, while this improvement declined after 500 K in the case of the highest annealing temperature. For such a sample, a metallic behavior was seen. The sample annealed at 1200 °C possessed the highest conductivity and the lowest activation energy. The impedance measurements were in good agreement with the conductivity plots and confirmed the emergence of a grain boundary effect with the increase in annealing temperature. For the sample annealed at the highest temperature, Z′ decreased rapidly with frequency. This sample exhibited the lowest defect density than the other samples. Consequently, its electrical conductivity increased. A Nyquist diagram was used to examine the contribution of the grains and grain boundary to conduction and to model each sample by an equivalent electrical circuit. The dielectric behavior of the investigated samples was correlated to the polarization effect.